Research Items (50)
Background Human papillomavirus (HPV) is the most common sexually transmitted infection globally. High-risk HPV types can cause cervical cancer, other anogenital cancer, and oropharyngeal cancer; low-risk HPV types can cause genital warts. Cervical cancer is highly preventable through HPV vaccination and screening; however, a lack of awareness and knowledge of HPV and these preventive strategies represents an important barrier to reducing the burden of the disease. The rapid development and widespread use of mobile technologies in the last few years present an opportunity to overcome this lack of knowledge and create new, effective, and modern health communication strategies. Objective This study aimed to describe the development of a mobile app called FightHPV, a game-based learning tool that educates mobile technology users about HPV, the disease risks associated with HPV infection, and existing preventive methods. Methods The first version of FightHPV was improved in a design-development-evaluation loop, which incorporated feedback from a beta testing study of 40 participants, a first focus group of 6 participants aged between 40 and 50 years and a second focus group of 23 participants aged between 16 and 18 years. Gameplay data from the beta testing study were collected using Google Analytics (Google), whereas feedback from focus groups was evaluated qualitatively. Of the 29 focus group participants, 26 returned self-administered questionnaires. HPV knowledge before and after playing the game was evaluated in the 22 participants from the second focus group who returned a questionnaire. Results FightHPV communicates concepts about HPV, associated diseases and their prevention by representing relationships among 14 characters in 6 episodes of 10 levels each, with each level being represented by a puzzle. Main concepts were reinforced with text explanations. Beta testing revealed that many players either failed or had to retry several times before succeeding at the more difficult levels in the game. It also revealed that players gave up at around level 47 of 60, which prompted the redesign of FightHPV to increase accessibility to all episodes. Focus group discussions led to several improvements in the user experience and dissemination of health information in the game, such as making all episodes available from the beginning of the game and rewriting the information in a more appealing way. Among the 26 focus group participants who returned a questionnaire, all stated that FightHPV is an appealing educational tool, 69% (18/26) reported that they liked the game, and 81% (21/26) stated that the game was challenging. We observed an increase in HPV knowledge after playing the game (P=.001). Conclusions FightHPV was easy to access, use, and it increased awareness about HPV infection, its consequences, and preventive measures. FightHPV can be used to educate people to take action against HPV and cervical cancer.
Objective: Women's contraceptive use at first sexual intercourse (FSI) may be associated with subsequent sexual behaviors. We examined associations between contraceptive methods used at FSI and subsequent number of lifetime partners, induced abortions and sexually transmitted infections (STIs). Study design: During 2011–2012, we collected questionnaire data from a random sample of women aged 18–45 years from Denmark, Norway and Sweden. We used logistic regression and discrete-time proportional hazards models to estimate odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals (CIs), comparing different contraceptive methods used at FSI in the whole study sample and in women with FSI in 2001 or later [when emergency contraceptive pills (ECPs) were available without prescription]. Results: Of 45,361 women in the study sample, those who did not use contraception at FSI (n=8155; 18.0%) were more likely than condom users to have ≥11 lifetime partners (OR=1.34; 95% CI 1.27–1.42), induced abortions (HR=1.62; 95% CI 1.53–1.71) and STIs (HR=1.15; 95% CI 1.10–1.20). ECP users (n=440, 1.0%) were more likely than condom users to have ≥11 lifetime partners (OR=1.76; 95% CI 1.40–2.22), induced abortions (HR=1.44; 95% CI 1.11–1.86) and STIs (HR=1.84; 95% CI 1.56–2.16). A similar pattern was seen in safe periods/withdrawal users. The associations did not change among women with FSI in 2001 or later (n=14,445). Conclusions: Compared with condom use, contraceptive nonuse, safe periods/withdrawal use and ECP use at FSI were associated with subsequent number of sexual partners, induced abortions and STIs. Implications: Contraceptive method used at first intercourse was associated with subsequent sexual behaviors in women. This study highlights the importance of early sexual behaviors and may help understand patterns of women's sexual behaviors.
It is valuable to establish a population‐based prevaccination baseline distribution of human papillomavirus (HPV) types among women with high‐grade cervical intraepithelial neoplasia (CIN) grade 2 or 3 and cervical cancer in order to assess the potential impact of HPV vaccination. In four countries (Denmark, Norway, Sweden, and Iceland), we collected consecutive series of cervical cancers (n = 639) and high‐grade precancerous cervical lesions (n = 1240) during 2004‐2006 before implementation of HPV vaccination and subjected the specimens to standardized HPV genotyping. The HPV prevalence was 82.7% (95% confidence interval [CI] 79.0‐86.4) in CIN2, 91.6% (95% CI 89.7‐93.5) in CIN3, and 86.4% (95% CI 83.7‐89.1) in cervical cancer. The most common HPV types in CIN2/3 were HPV16 (CIN2: 35.9%, 95% CI 31.2‐40.6; CIN3: 50.2%, 95% CI 46.8‐53.6) and HPV31 (CIN2: 10.9%, 95% CI 7.8‐13.9; CIN3: 12.1%, 95% CI 9.9‐14.3), while HPV16 and HPV18 were the most frequent types in cervical cancer (48.8%, 95% CI 44.9‐52.7 and 15.3%, 95% CI 12.5‐18.1, respectively). The prevalence of HPV16/18 decreased with increasing age at diagnosis in both CIN2/3 and cervical cancer (P < 0.0001). Elimination of HPV16/18 by vaccination is predicted to prevent 42% (95% CI 37.0‐46.7) of CIN2, 57% (95% CI 53.8‐60.5) of CIN3 and 64% (95% CI 60.3‐67.7) of cervical cancer. Prevention of the five additional HPV types HPV31/33/45/52/58 would increase the protection to 68% (95% CI 63.0‐72.2) in CIN2, 85% (95% CI 82.4‐87.2) in CIN3 and 80% (95% CI 77.0‐83.2) in cervical cancer. This study provides large‐scale and representative baselines for assessing and evaluating the population‐based preventive impact of HPV vaccination.
From 2015, Norway has implemented high‐risk human papilloma virus (hrHPV) testing in primary screening for cervical cancer. Women 34‐69 years, living in four counties, have been pseudo‐randomly assigned (1:1 randomization) to either hrHPV testing every 5 years (followed by cytology if hrHPV positive), or cytology testing every 3 years (followed by hrHPV testing if low‐grade cytology is detected). We compared anxiety and depression scores among participants by screening arm and results. 1,008 women answered a structured questionnaire which included the validated Patient Health Questionnaire‐4 (PHQ‐4). The Relative Risk Ratio (RRR) of mild vs normal anxiety and depression scores, and moderate/severe vs normal anxiety and depression scores, were estimated by multinomial logistic regression with 95% confidence intervals (95% CI). Compared to women who were screened with cytology, women randomized to hrHPV testing were not more likely to have mild anxiety and depression scores (RRR 0.96, CI 0.70‐1.31) nor more likely to have moderate/severe anxiety and depression scores (RRR 1.14, CI 0.65‐2.02). Women with five different combinations of abnormal screening test results were not more likely to have mild or moderate/severe vs normal anxiety and depression scores than women with normal screening results. The likelihood of having abnormal long‐term (4 to 24 months after the screening) anxiety or depression scores among women 34 years and older was not affected by screening method or screening results. The results of this study suggest that a change to hrHPV testing in primary screening would not increase psychological distress among participants. This article is protected by copyright. All rights reserved.
- May 2018
Objective: To monitor the changes in prevalence of human papillomavirus (HPV) infections in women <50 years of age, participating in cervical screening programs of Denmark, Norway, and Sweden, before and after introduction of quadrivalent HPV (qHPV) vaccination. Methods: Liquid-based cytology samples were collected from 6538 women who attended cervical screening in Denmark, Norway, and Sweden in 2006-2008 and from 6332 similarly enrolled women in 2012-2013. Denmark started organized qHPV vaccination in 2008, Norway in 2009, and Sweden in 2012. All HPV testing and genotyping was performed using identical enrollment and analysis methods, by accredited general primer polymerase chain reaction methods with typing using the Luminex system. Results: Overall HPV positivity declined slightly from 36.5% in 2006-2008 to 34.5% in 2012-2013. The decline was most pronounced among women 18-26 years of age: from 54.4% to 48.1% (P < 0.001). The decline was substantial for vaccine HPV types (HPV6/11/16/18: decline from 22.3% to 16.6%; P < 0.001) and was seen for both low-risk vaccine types (HPV6/11 declined from 5.0% to 2.5%) and high-risk vaccine types (HPV16/18 declined from 18.9% to 14.9%). Among women 27-50 years of age, there was no change between the time periods (22.5% and 21.6%, respectively). The significant decline in the younger age group was different in the 3 countries. Conclusion: This population-based study enrolling >12,000 women participating in cervical screening in the 3 Nordic countries before and after introduction of organized qHPV vaccination demonstrated a marked decline in HPV infection in the younger population in the 2 countries where qHPV vaccination programs started in 2008-2009, suggesting that organized HPV vaccination programs resulted in a decrease of HPV types circulating in the general population.
- Mar 2018
Objective This study examined the associations between current behaviours/characteristics and self-perceived risk for STIs, among randomly selected women aged 18–45 years from Denmark, Norway and Sweden. Method A population-based, cross-sectional, questionnaire study (paper based, web based and telephone based) was conducted during 2011–2012. We compared medium–high STI risk perception with no/low risk perception. The associations were explored for women who had ever had sexual intercourse and for women with a new partner in the last 6 months using multivariable logistic regression. Result The overall prevalence of medium–high STI risk perception was 7.4%. It was highest among women aged 18–24 years (16.2%) and among the Danish women (8.8%). Number of new sexual partners in the last 6 months (≥3vs 0 partners, OR 14.94, 95% CI 13.20 to 16.94) was strongly associated with medium–high STI risk perception. Among women with a new partner in the last 6 months, lack of condom use increased medium–high STI risk perception (OR 1.73, 95% CI 1.52 to 1.96). Genital warts in the last year, binge drinking and being single were associated with increased risk perception and remained statistically significant after additional adjustments were made for number of new partners and condom use with new partners in the last 6 months. Conclusion Subjective perception of risk for STI was associated with women’s current risk-taking behaviours, indicating women generally are able to assess their risks for STIs. However, a considerable proportion of women with multiple new partners in the last 6 months and no condom use still considered themselves at no/low risk for STI.
Objectives Examine long-term incidence trends of human papillomavirus (HPV)-related cancer in Norway, and estimate the number of cancer cases preventable by vaccines against HPV 16/18 or HPV 16/18/31/33/45/52/58. Design Observational registry-based study. We extracted incident cases of HPV-related cancer during 1953–2015 from the Cancer Registry of Norway. Tumour HPV prevalence estimates from large international meta-analyses or from Norway were used to estimate the protective potential of HPV vaccines. Participants and setting The Norwegian population. Primary outcome measures Incidence trend analyses during 1953–2015 for squamous cell carcinoma (SCC) of the cervix, vulva, vagina, oropharynx, anus and penis, and adenocarcinoma of the cervix. Additionally, the number of cancer cases preventable by HPV vaccination. Results Among women, incidences of SCC of the anus, oropharynx, vulva and cervical adenocarcinoma increased, while vaginal SCC showed no trend. For these cancers combined, the average annual percentage change (AAPC) during 1953–2015 was 1.2 (95% CI 0.7 to 1.6). The incidence of cervical SCC generally decreased during 1976–2004 and remained stable thereafter. Among men, incidences of SCC of the anus, oropharynx and penis increased. The AAPC during 1953–2015 combined for all male HPV-related cancer was 1.9 (95% CI 1.3 to 2.5). A vaccine against HPV 16/18 might yearly prevent 402 (95% CI 382 to 420) cancers. A vaccine against HPV 16/18/31/33/45/52/58 might yearly prevent 478 (95% CI 464 to 490) cancers, of which 206 (95% CI 202 to 209) occur in non-cervical organs, and 113 (95% CI 110 to 115) occur among men. Conclusions The incidences of HPV-related cancers that are not effectively prevented by screening have generally increased during 1953–2015. HPV vaccination can prevent a substantial number of cancers in Norway, in cervical and non-cervical organs, among women and men.
- Dec 2017
Background: In Norway, snus use among women has increased substantially over the last decade, particularly in younger age groups. Snus use is associated with increased morbidity among men, but few studies have addressed health consequences of snus use among women. Aim: To investigate the associations between body mass index (BMI) and female snus use, and between self-rated general health and female snus use. Methods: A nationally representative net sample of 13,756 women in Norway, aged 18-45 years, participated in a survey on lifestyle and health. Ordinal logistic regression was applied to address associations between snus use and BMI/general health, adjusting for age and lifestyle factors. Results: Compared to never users of snus, daily snus users had a lower likelihood of high BMI (OR: 0.83, 95% CI: 0.68-1.00), a higher likelihood of low BMI (OR: 1.63, 95% CI: 1.14-2.33), and a higher likelihood of poor/fair health (OR: 1.43, 95% CI: 1.08-1.90). Former and occasional snus users did not differ from never users in terms of BMI or general health in multiply adjusted models. Daily smokers had the highest likelihood of reporting poor/fair health (OR: 2.18, 95% CI: 1.8-2.63) relative to never smokers. Conclusions: Daily female snus use was associated with a lower likelihood of being overweight, and a higher likelihood of being underweight. Moreover, daily snus use was associated with a higher likelihood of worse general health. Former and occasional female snus use was not associated with BMI or general health.
We examine trends in incidence, mortality and survival of penile squamous cell carcinoma (SCC) in Norway over 60 years. Data on all cases of penile cancer diagnosed in Norway during 1956-2015 was obtained from the Cancer Registry of Norway. Trends in age-standardised rates of penile SCC incidence, mortality and 5-year relative survival were assessed by the annual percentage change statistic and joinpoint regression. A total of 1596 penile cancer cases were diagnosed during 1956-2015, among which 1474 (92.4%) were SCC. During 2011-2015, the age-standardised incidence and mortality of penile SCC were 0.91 (95% confidence interval (CI): 0.78;1.05) and 0.50 (0.42;0.60) per 100,000, respectively, and the 5-year relative survival was 61.6% (41.9;76.4). The incidence of SCC increased during 1956-2015, with an average annual percentage change (AAPC) of 0.80% (0.46;1.15). The increase was strongest among men diagnosed at a relatively early age (age<=64 years; AAPC: 1.47% (0.90;2.05)). Mortality also increased over the study period (AAPC: 0.47% (0.10;0.85)), whereas 5-year relative survival did not change (AAPC: 0.08% (-0.19; 0.36)). We conclude that the incidence of penile SCC has increased at a moderate and constant rate during 1956-2015, and that the most consistent increase occurred among younger men. Mortality also increased during the study period. However, survival did not change, thus changes in diagnostics and treatment had little impact on survival from penile SCC. Since a substantial proportion of penile SCC is caused by human papillomavirus (HPV), the incidence increase may in part be attributed to increased exposure to HPV in the population. This article is protected by copyright. All rights reserved.
- Oct 2017
Background The long-term effectiveness of the quadrivalent human papillomavirus (qHPV) vaccine was assessed by monitoring the combined incidence of cervical intraepithelial neoplasia (CIN2, CIN3), adenocarcinoma in situ (AIS), and cervical cancer related to HPV16 or HPV18. Methods Women from Nordic countries of Denmark, Iceland, Norway, and Sweden who received a 3-dose regimen of the qHPV vaccine in the beginning of FUTURE II (Females United to Unilaterally Reduce Endo/Ectocervical Disease; V501-015, base study NCT00092534) are followed through different national registries. Effectiveness analyses were conducted approximately 2 years following completion of the base study and occur approximately every 2 years thereafter for 10 years (ie, 14 years from day 1 of the base study). Vaccine effectiveness against HPV16/18-related CIN2 or worse (CIN2+) was estimated by comparing the observed incidence with the expected incidence of CIN2+ in an unvaccinated cohort using historical registry data. Results In the per-protocol population (2084 women) analysis of effectiveness after the first 12 years, there were no breakthrough cases of HPV16/18 CIN2+ after 9437 person- years of follow-up. Statistical power was sufficient to conclude that qHPV vaccine effectiveness remains above 90% for at least 10 years. The number of person-years during the follow-up interval of 10–12 years is continuing to accrue and shows a trend toward continuing effectiveness of the vaccine during that period. Conclusion The qHPV vaccine shows continued protection in women through at least 10 years, with a trend for continued protection through 12 years of follow-up. Clinical Trials Registration NCT00092534. Study Identification V501-015
- Dec 2016
Introduction: To describe recent patterns of contraceptive use at first sexual intercourse (FSI) and to examine whether selected factors are associated with non-use and emergency contraceptive pill (ECP) use at FSI, among 18-26-year-old women from Denmark, Norway and Sweden. Material and methods: This was a population-based, questionnaire study of randomly chosen 18-26-year-old Scandinavian women. The prevalence of contraception methods used at FSI was calculated. Factors associated with contraceptive non-use and ECP use at FSI were determined using log binomial models. Results: The prevalence of contraceptive non-use and ECP use was lowest in Denmark (9.6% % and 2.1%, respectively) compared with Norway (14.1% and 4.4%) and Sweden (16.6% and 4.5%). The risk of contraceptive non-use increased in women who had FSI at or before 14 years of age (13-14 years: PR 1.40; 95% CI 1.24-1.58). The risk of both non-use and ECP use increased when the partner at FSI was 20 years or older and with increasing age difference between the partner and the woman at her FSI. Smoking initiation prior to FSI increased risk of contraceptive non-use (PR 1.70; 95% CI 1.50-1.92), while alcohol initiation prior to FSI increased risk of ECP use at FSI (PR 1.95; 95% CI 1.49-2.54). Conclusions: Contraceptive non-use at FSI was strongly associated with early age at FSI. ECP and contraceptive non-use at FSI were both strongly associated with increasing partner age and an increasing difference in age between the woman and her partner. Hence, young women should be educated to negotiate contraceptive use with their partners. This article is protected by copyright. All rights reserved.
High coverage is essential for an effective screening programme. Here we present screening barriers and facilitators among 1.3 million women aged 25–69years eligible for screening within the Norwegian Cervical Cancer Screening Program (NCCSP). We defined non-adherence as no screening test in 2008–2012. We divided adherent women into those screened spontaneously, and those who had a smear after receiving a reminder from the NCCSP. Explanatory variables were extracted from several nationwide registers, and modelled by modified Poisson regression. In total, 34% of women were non-adherent. 31% of native Norwegians were non-adherent, compared to 50% of immigrants. Immigrant status was a strong predictor of non-adherence, but the vast majority of non-adherent women were still native Norwegians. Higher non-adherence rates were associated with having a male general practitioner (GP), a foreign GP, a young GP, and distance to the screening site. Being unmarried, having no children, having lower socioeconomic position and region of residence predicted non-adherence and, to a smaller extent, reminded adherence to screening. In contrast, previous experience with cervical abnormalities substantially increased adherence to screening. The population-based screening programme promotes equity by recruiting women who are less likely to participate spontaneously. However, socioeconomic disparities were evident in a country with a nationwide programme and a policy of equal access to health care. Initiatives aimed at removing practical and financial barriers to equitable screening delivery and at reducing the effect of sociodemographic attributes on screening participation are needed.
Uptake of the HPV vaccine has been lower than the uptake of most other childhood vaccines offered in public programs. Since the HPV vaccine protects against a sexually transmitted virus, one barrier to uptake specific to the HPV vaccine may be the concern that vaccination may encourage risky sexual behaviour. Unanimous findings from recent studies show that HPV vaccination does not lead to sexual risk compensation, which is an important message to parents, clinicians and other decision-makers regarding HPV vaccination. Some issues remain to be investigated, like HPV vaccination and sexual risk compensation among boys.
Using a large, population-based survey, we assessed the levels and correlates of human papillomavirus (HPV) awareness among Scandinavian women after introduction of HPV vaccination. In 2011-2012, a random sample of women aged between 18 and 45 years from Denmark, Sweden and Norway received a questionnaire on lifestyle, health and HPV awareness. We included 47 895 women (response rate 60.6%) in our study. Country-specific and age-specific proportions of women who had heard of HPV in 2011-2012 (postvaccination survey) were compared with corresponding proportions in an identical survey from 2004-2005 (prevaccination survey, n=54 079, response rate 71.3%). Correlates of HPV awareness in the postvaccination survey were assessed by logistic regression. In all countries and age groups, awareness of HPV increased from the prevaccination to the postvaccination survey. In the postvaccination survey, HPV awareness was higher in Denmark (75.8%) and Sweden (74.8%) compared with Norway (62.4%), with greatest discrepancy among women aged between 18 and 19 years (Denmark: 74.9%, Sweden: 70.4%, Norway: 39.6%). Variables associated with low HPV awareness included the following: low education [<=12 vs. >16 years of schooling: odds ratio (OR)=0.45, 95% confidence interval (CI): 0.42-0.48], being a virgin (vs. nonvirgins: OR=0.74, 95% CI: 0.66-0.83), never having used condoms (vs. ever: OR=0.62, 95% CI: 0.56-0.67), nonuse of contraception at first intercourse (vs. use: OR=0.83, 95% CI: 0.79-0.88) and daily smoking (vs. never: OR=0.86, 95% CI: 0.80-0.92). HPV awareness in Scandinavia has increased since the introduction of HPV vaccination. However, 24-38% of Scandinavian women still have never heard of HPV. Future information efforts should target groups with low HPV awareness. Copyright
The objective of this study was to assess the reciprocal association between non-Hodgkin lymphoma (NHL) and Merkel cell carcinoma (MCC) using the data of four Nordic Cancer Registries. Data for this study were drawn from the Danish, Finnish, Norwegian, and Swedish cancer registries. Standardized incidence ratios (SIRs) for MCC among NHL patients, and for NHL among MCC patients, were calculated. There were 109838 individuals with NHL and 1411 individuals with MCC, of which 28 had joint occurrence of NHL and MCC. In 18 cases, NHL was diagnosed first, and in 10 cases, MCC was diagnosed first. The SIR for MCC after NHL was 4.34 (95% confidence interval 2.57 - 6.85). The SIR for NHL after MCC was 3.13 (1.50 - 5.77). Although the absolute frequency of joint occurrence of MCC and NHL is low, individuals suffering from one of the cancer forms have an increased risk of the other.
- Jun 2015
While smoking in Norway has become less prevalent, snus use has increased, including among women. The aims of this study were to describe female snus use and its correlates, and to contrast patterns of snus use and smoking. In 2011-2012, data on tobacco use, age, education, alcohol consumption, sexual behaviours, and physical activity were collected from a population based sample of 13,756 Norwegian women aged 18-45 years, using a self-administered questionnaire. Ever-use prevalence of snus ranged from 29.6% to 4.5% among those aged 18-19 years and 40-45 years, respectively. In contrast, the corresponding figures for smoking was 24.1% and 44.1%. Among snus users, 54.1% and 22.8% of 18-19 and 40-45 year-olds had never smoked, respectively. Debut age for snus use increased markedly with age, and was higher than debut age for smoking. Female snus use was positively associated with intermediate education, alcohol consumption, number of sexual partners, and hard physical activity. Smoking was also positively associated with alcohol consumption and number of sexual partners, but negatively associated with physical activity and education. While most snus users among older women were former or current smokers, this was not the case among younger women. Low snus debut age and extensive snus use among younger women suggest that measures to reduce snus use should be targeted at young adolescents. The correlates of female snus use and smoking were not identical, and were similar to those previously documented for men. © The Author 2015. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: email@example.com.
To assess demographic, socioeconomic and behavioural correlates of HPV vaccination of preadolescent girls in a publicly funded, school-based vaccination programme. Data for all Norwegian girls born 1997-1999, eligible for routine school-based HPV vaccination in 2009-2011 (n=90,842), and their registered mother and father, were merged from national registries. Correlates of girl vaccination status were analysed by unadjusted and multivariable logistic regression. In total, 78.2% of the girls received the first dose of the HPV vaccine, 74.6% received three doses, and 94.8% received the MMR vaccine. Correlates associated with initiation of HPV vaccination included parental age, income and education, maternal occupational status and cervical screening attendance, and girl receipt of the MMR vaccine. Rates of completion of HPV vaccination among initiators were high, and disparities in completion were negligible. Maternal and paternal correlates of daughter HPV vaccination status were similar. Routine school-based vaccination generally provides equitable delivery, yet some disparities exist. Information campaigns designed to reach the sub-groups with relatively low vaccine uptake could reduce disparities. In none of the sub-groups investigated did uptake of the HPV vaccine approach that of the MMR vaccine, further demonstrating a general potential for improvement in HPV vaccine uptake. Copyright © 2015. Published by Elsevier Inc.
- Apr 2015
Both major morphologic types of cervical cancer, squamous cell carcinoma (SCC) and adenocarcinoma (AC), are causally related to persistent infection with high risk human papillomavirus (hrHPV), but screening has primarily been effective at preventing SCC. We analysed incidence trends of cervical cancer in Norway stratified by morphologies over 55 years, and projected SCC incidence in the absence of screening by assessing the changes in the incidence rate of AC. The Cancer Registry of Norway was used to identify all 19,530 malignancies in the cervix diagnosed in the period 1956-2010. The majority of these (82.9%) were classified as SCCs, 10.5% as ACs, and the remaining 6.6% were of other or undefined morphology. By joint-point analyses of a period of more than five decades, the average annual percentage change of the age-standardised incidence was -1.0 (95%CI:-2.1,0.1) for cervical SCC, and 1.5 (95%CI:1.1,1.9) for cervical AC, and -0.9 (95%CI:-1.4,-0.3) for cervical cancers of other or undefined morphology. The projected age-standardised incidence rate of cervical SCC in Norway, assuming no screening, was 28.6 per 100,000 woman-years in 2010, which compared to the observed SCC rate of 7.3 corresponds to an estimated 74% reduction in SCC, or a 68% reduction due to screening in the total cervical cancer burden. Cytology screening has impacted cervical cancer burden more than suggested by the overall observed cervical cancer incidence reduction since its peak in the mid-1970s. The simultaneous substantial increase in cervical adenocarcinoma in Norway is presumably indicative of an increase in exposure to HPV over time. This article is protected by copyright. All rights reserved. © 2015 UICC.
Objective: To assess whether recipients and non-recipients of the human papillomavirus (HPV) vaccine subsequently differ in terms of sexual risk taking behaviour. Design: Cross-sectional survey. Sequential analyses constructed from self-reported age at vaccination, age at first intercourse and age at response. Setting: A random selection of women aged 18-46 years living in Denmark, Norway and Sweden in 2011-2012, eligible for opportunistic or organized catch-up HPV vaccination. Participants: A total of 3805 women reported to have received the HPV vaccine and 40,247 reported not to have received it. Among vaccinees, 1539 received the HPV vaccine before or at the same age as sexual debut, of which 476 and 1063 were eligible for organized catch-up and opportunistic vaccination, respectively. Main outcome measures: Self-reported sexual behaviour, compared by hazard ratios and odds ratios for women who received the HPV vaccine before or at the same age as sexual debut versus women who did not receive the HPV vaccine. Results: HPV vaccination did not result in younger age at first intercourse. Women who received the HPV vaccine before or at the same age as sexual debut did not have more sexual partners than did non-vaccinees. Non-use of contraception during first intercourse was more common among non-vaccinees than among HPV vaccinees. The results were similar for organized catch-up and opportunistic vaccinees. Conclusion: Women who received the HPV vaccine before or at the same age as sexual debut did not subsequently engage more in sexual risk taking behaviour than women who did not receive the HPV vaccine.
Background: Infection with high-risk human papillomavirus (HPV) is causally related to cervical, vulvar and vaginal pre-invasive neoplasias and cancers. Highly effective vaccines against HPV types 16/18 have been available since 2006, and are currently used in many countries in combination with cervical cancer screening to control the burden of cervical cancer. We estimated the overall and age-specific incidence rate (IR) of cervical, vulvar and vaginal cancer and pre-invasive neoplasia in Denmark, Iceland, Norway and Sweden in 2004-2006, prior to the availability of HPV vaccines, in order to establish a baseline for surveillance. We also estimated the population attributable fraction to determine roughly the expected effect of HPV16/18 vaccination on the incidence of these diseases. Methods: Information on incident cervical, vulvar and vaginal cancers and high-grade pre-invasive neoplasias was obtained from high-quality national population-based registries. A literature review was conducted to define the fraction of these lesions attributable to HPV16/18, i.e., those that could be prevented by HPV vaccination. Results: Among the four countries, the age-standardised IR/10⁵ of cervical, vaginal and vulvar cancer ranged from 8.4-13.8, 1.3-3.1 and 0.2-0.6, respectively. The risk for cervical cancer was highest in women aged 30-39, while vulvar and vaginal cancers were most common in women aged 70+. Age-standardised IR/10⁵ of cervical, vulvar and vaginal pre-invasive neoplasia ranged between 138.8-183.2, 2.5-8.8 and 0.5-1.3, respectively. Women aged 20-29 had the highest risk for cervical pre-invasive neoplasia, while vulvar and vaginal pre-invasive neoplasia peaked in women aged 40-49 and 60-69, respectively. Over 50% of the observed 47,820 incident invasive and pre-invasive cancer cases in 2004-2006 can be attributed to HPV16/18. Conclusion: In the four countries, vaccination against HPV 16/18 could prevent approximately 8500 cases of gynecological cancer and pre-cancer annually. Population-based cancer and vaccination registries are essential to assess the predicted public health effects of HPV vaccination.
Background: Human papillomavirus and hormonal contraceptives may be risk factors for cervical precancer and malignant breast tumours. Methods: Standardised incidence ratios (SIRs) of malignant breast tumours during 1970–2008 were estimated separately for women with prior squamous and glandular cervical precancer. Results: Women with squamous precancer and women with glandular precancer in the cervix had a significantly higher risk of malignant breast tumours than the general female population (SIR, 95% confidence interval: 1.10, 1.05–1.14 and 1.52, 1.11–2.08, respectively). Interpretation: Shared risk factors or screening attendance may explain the excess risk of malignant breast tumours among women with a history of cervical precancer.
A crucial factor concerning the utility of Cancer Registries is the data quality with respect to comparability, completeness, validity and timeliness. However, the data quality of the registration of premalignant lesions has rarely been addressed. High grade vulvar intraepithelial neoplasia (VIN) and vaginal intraepithelial neoplasia (VaIN) are premalignant lesions which may develop into cancer, and are often associated with infection with the human papillomarvirus (HPV). The aim was to evaluate the quality of registration of VIN and VaIN at the Cancer Registry of Norway (CRN). We re-collected all notifications with high grade VIN and VaIN diagnoses during 2002 to 2007 from pathology laboratories, and compared these to the data in the CRN database so as to quantitatively measure the completeness, validity and timeliness of the data. Over the period 2002 to 2007 we estimated the completeness of the 1556 VIN and 297 VaIN notifications to be 95.0% and 92.9%, respectively. The original and reabstracted topography codes showed major discrepancies for 12 of 642 (1.9%) VIN and 7 of 128 (5.5%) VaIN notifications. The original and reabstracted morphology codes for VIN and VaIN were identical for 724 out of 814 notifications. Sixteen notifications had a major discrepancy. For the period 2002 to 2007 the median time elapsed between date of diagnosis and date of registration were 436 and 441 days for VIN and VaIN cases, respectively. Based on the present analysis of the comparability, completeness, validity and timeliness of premalignant lesions of vulva and vagina, we conclude that the Cancer Registry of Norway is able to monitor such premalignant lesions satisfactorily.
- Aug 2011
The aim of this study was to assess the prevalence of women reporting ever having genital chlamydia, genital herpes, Trichomonas vaginalis, and gonorrhea, and to identify factors associated with each of these sexually transmitted infections (STIs). The study was based on a large cross-sectional survey conducted in 2004-2005 among randomly sampled women (18-45 years) from the computerized population registries in Denmark, Iceland, Norway, and Sweden. A total of 69,567 women were included in the study. The overall prevalence in Denmark, Iceland, Norway, and Sweden was 1.5% for reporting ever having had Trichomonas vaginalis, 1.9% for gonorrhea, 4.8% for genital herpes, and 17.0% for genital chlamydia. The prevalence of each of these STIs varied with birth cohort and country. In addition, they were strongly associated with lifetime number of partners and having a previous diagnosis of another sexually transmitted infection. Moreover, a diagnosis of genital chlamydia or gonorrhea was associated with early age at first intercourse and smoking initiation. Finally, reporting genital chlamydia was associated with early age at drinking initiation, and ever use of hormonal contraceptives and condoms. Genital chlamydia occurs frequently among women in the Nordic countries. Risk-taking behavior, particularly sexual behavior, is strongly associated with STIs, which suggest that further information is needed about STIs and their consequences, targeting high-risk groups. There is also a need for continued monitoring of STIs in order to follow the prevalence and to gain further knowledge about risk factors.
Risk-taking behaviours such as early initiation of smoking, alcohol drinking and sexual activity often cluster within individuals and could be characteristics of adolescents who in general are risk takers. In the present study, using a large population-based sample of 64 659 women aged 18-45 years in four Nordic countries, we investigate whether young age at first sexual intercourse is associated with subsequent risk-taking behaviours. We examined the association between young age at first sexual intercourse (age ≤14 years) and subsequent risk-taking behaviours by using multivariate logistic regression by which odds ratios (ORs) and the corresponding 95% confidence intervals (95% CIs) were estimated. The OR of reporting more than 10 lifetime sexual partners was almost four times higher among women who reported a young age at first intercourse (OR = 3.79; 95% CI: 3.60-4.00) in comparison with women >14 years at first intercourse. Furthermore, women who were young at first intercourse were more likely to report two or more recent partners (OR = 1.67; 95% CI: 1.54-1.82) and to have a history of STIs (OR = 2.03; 95% CI: 1.93-2.13). In addition, young age at first intercourse was associated with current smoking (OR = 2.31; 95% CI: 2.20-2.43) and binge drinking (OR = 1.36; 95% CI: 1.28-1.44). All ORs were adjusted for age, years of education and country of residence. Young age at first intercourse is associated with subsequent risk-taking behaviours. Our study emphasizes the importance of targeting prevention efforts towards the complexity of risk-taking behaviours.
Cervical cancer incidence and mortality may be reduced by organized screening. Participant compliance with the attendance recommendations of the screening program is necessary to achieve this. Knowledge about the predictors of compliance is needed in order to enhance screening attendance. The Norwegian Co-ordinated Cervical Cancer Screening Program (NCCSP) registers all cervix cytology diagnoses in Norway and individually reminds women who have no registered smear for the past three years to make an appointment for screening. In the present study, a questionnaire on lifestyle and health was administered to a random sample of Norwegian women. The response rate was 68%. To address the predictors of screening attendance for the 12,058 women aged 25-45 who were eligible for this study, individual questionnaire data was linked to the cytology registry of the NCCSP. We distinguished between non-attendees, opportunistic attendees and reminded attendees to screening for a period of four years. Predictors of non-attendance versus attendance and reminded versus opportunistic attendance were established by multivariate logistic regression. Women who attended screening were more likely than non-attendees to report that they were aware of the recommended screening interval, a history of sexually transmitted infections and a history of hormonal contraceptive and condom use. Attendance was also positively associated with being married/cohabiting, being a non-smoker and giving birth. Women who attended after being reminded were more likely than opportunistic attendees to be aware of cervical cancer and the recommended screening interval, but less likely to report a history of sexually transmitted infections and hormonal contraceptive use. Moreover, the likelihood of reminded attendance increased with age. Educational level did not significantly affect the women's attendance status in the fully adjusted models. The likelihood of attendance in an organized screening program was higher among women who were aware of cervical screening, which suggests a potential for a higher attendance rate through improving the public knowledge of screening. Further, the lower awareness among opportunistic than reminded attendees suggests that physicians may inform their patients better when smears are taken at the physician's initiative.
The cognitive processes of predators play a central role in the evolution of prey characters. Numerous studies have shown that vertebrate predators may learn to associate the characteristics of prey (e.g. color) with the cost or benefit of ingesting them, thus forming preferences and aversions for different kinds of prey. Although the distribution and quality of prey types can differ between environmental contexts, which may make it profitable to attack a prey type in some contexts but not in others, the influence of environmental cues in decisions to attack has rarely been addressed. Recent theory suggests that modification of prey preferences by environmental cues such as microhabitat or temperature may influence the evolution of prey characteristics. Here, we show that the environmental foraging context may determine prey choice in great tits (Parus major) through learned association between the prey phenotype (appearance and palatability) and a contextual background cue. The same individuals were able to learn and maintain two different sets of food preferences and aversions for use in two different environmental contexts (aviaries with red or blue wooden boards), indicating a role for contextual learning in vertebrate foraging behavior. KeywordsPredator psychology-Cognitive ecology-Contextual learning-Associative learning-Prey preferences-Sex difference
To assess the association between smoking and the reported clinical diagnosis of genital warts. A sample of 58,094 women (aged 18-45) randomly drawn from the general female population of Denmark, Iceland, Norway and Sweden answered a questionnaire on lifestyle and health. Longitudinal data were reconstructed based on self report of age-specific events. In a Cox regression model, women who reported having been clinically diagnosed with genital warts were followed up until the age at first diagnosis, while women who reported never having been diagnosed with genital warts were censored at the age of interview. Age-specific smoking doses and ages at onset of smoking, sexual intercourse, condom use, hormonal contraceptive use, first pregnancy and alcohol drinking were included in the model as time-dependent covariates. The model also included lifetime number of coital partners and country of origin as fixed covariates. Ever-smokers reported a lower age at first intercourse and more coital partners than never-smokers. The adjusted model showed that sexual behaviour strongly influenced the risk of being diagnosed with genital warts, and that smokers in addition had an increased risk compared with non-smokers (adjusted HR=1.27, 95% CI 1.17 to 1.37). There was also a modest additional dose-response effect of smoking, with smokers experiencing a 0.6% increased risk of being diagnosed with genital warts for each additional cigarette smoked daily (adjusted HR=1.006, 95% CI 1.001 to 1.012). Smokers experienced a moderately increased risk of being diagnosed with genital warts. This finding could be explained by the immunosuppressive effects of nicotine, or by confounding not accounted for in the adjusted model.
- Mar 2010
To investigate associations between early smoking initiation, risk-taking behavior and reproductive health. A random sample of 69,486 women aged 18-45 from Denmark, Iceland, Norway and Sweden was surveyed in 2004-2005. We compared behavior and health among women who initiated smoking early (before age 15), later (at 15 or later) and never smokers. Adult women who initiated smoking early reported more lifetime and recent sexual partners and less condom use than women who initiated smoking later, and they had lower debut ages for coitus, pregnancy and alcohol consumption. Experiences of teenage pregnancy, abortion/miscarriage and having had at least one sexually transmitted infection (gonorrhea, herpes simplex, trichomonas vaginalis, chlamydia, genital warts) were more frequent among early than among later smoking initiators. Never smoking women reported fewer partners, later debut ages, and more condom use and were less likely to have experienced teenage pregnancy, abortion/miscarriage and having had at least one sexually transmitted infection than either group of smokers. Early smoking initiators were more likely to engage in risk-taking behavior and experience adverse reproductive events than were smokers who initiated later. Age at smoking initiation may be an indicator of future reproductive health. Early smoking initiators represent targets for reproductive health information.
- Feb 2010
Bird song is used to attract mates and deter rivals, and also functions as a species recognition cue. It is a flexible trait affected by learning, hence the choice of song tutors may affect an individuals' singing. By interspecifically cross-fostering great tits (Parus major) to blue tits (Cyanistes caeruleus) in the wild, we have manipulated the species recognition of great tits, which in turn has influenced their song. In the present study, we presented breeding great tit and blue tit control males with playback of the aberrant song of cross-fostered great tit males and playback of the normal song of control great tit males. Blue tit males responded more to cross-fostered than control great tit song while great tit males showed the inverse response pattern. This shows that interspecific cross-fostering may affect both inter- and intraspecific communication. However, the response of males of both species towards the song of cross-fostered great tit males was not of the same magnitude as the response towards ordinary blue tit song; thus, the real species identity is to some extent maintained in the aberrant song of cross-fostered males.
- Oct 2009
Mate guarding is thought to decrease the likelihood of cuckoldry and, hence, increase the fitness of guarding males. Mate guarding is costly for males and must be traded off with other fitness-enhancing behaviours. Over several years, we have cross-fostered great tits (Parus major) to blue tits (Cyanistes caeruleus) and this experimental treatment has influenced the mate and rival recognition of cross-fostered birds. Here we show that cross-fostered great tit males mate guard their females less than do control great tits, regardless of whether the cross-fostered males were mated to great tit females or cross-fostered blue tit females. Cross-fostered great tit males sang more and interacted more frequently with blue tit males than did controls. Females paired to males of the two groups did not differ in the extent to which they initiated movements away from their mates. We conclude that the altered species-assortative behaviour resulting from interspecific cross-fostering influences mate guarding in great tit males, probably by cross-fostered males increasing investment in territorial behaviour at the expense of mate guarding, and/or by cross-fostered males mate guarding less due to a reduced affinity for their female. Such trade-offs may have a general significance for mate guarding species.
- Sep 2009
Sex allocation theory states that parents should adjust their offspring sex ratio according to the expected fitness returns from sons and daughters. Several recent studies indicate that such adaptive manipulation of offspring sex ratio is achievable, and that it may be influenced by e.g. morphological characters. Here we manipulate behaviour through interspecific cross-fostering of great tits (Parus major) and blue tits (Cyanistes caeruleus), and investigate its effect on the offspring sex ratio of adults that were themselves cross-fostered as chicks. The experience of being raised by a different species has previously been shown to result in aberrant species assortative behaviour and song, and a lowered dominance status during winter. Brood sex ratios of conspecifically breeding pairs with and without cross-fostered members were compared. Broods with at least one cross-fostered parent contained significantly more males than did control broods. Sex of cross-fostered parents did not influence the brood sex ratio. We conclude that female great tits and blue tits seem to be able to adjust the sex ratio of their broods, and that changes in their own or their partners’ behaviour may elicit such adjustments.
- Mar 2008
Species recognition may be learned through imprinting early in life. Imprinting has normally been studied under highly unnatural conditions in the laboratory. We tested whether species recognition mediated through imprinting is individually modifiable in a field setting where great tits, Parus major, have been artificially cross-fostered to blue tits, Cyanistes caeruleus, and vice versa. We have shown previously that cross-fostered birds have deviant species recognition, in terms of both mate choice and aggressive responses towards rivals. Natural interactions among conspecifics and heterospecifics are common in these populations, potentially giving cross-fostered birds scope for relearning their species identity. We tested whether species recognition may change with experience during adulthood by comparing the aggressive response of cross-fostered birds and controls of different ages towards caged intruders. When breeding, cross-fostered birds responded aggressively towards same-sex individuals of their heterospecific foster species, while unmanipulated controls responded mainly towards conspecifics. We found that the aggressive response decreased with age at similar rates in both treatments and in both species. Moreover, there was no effect of age on the relative response towards conspecifics and heterospecifics in either treatment. Hence, we found no evidence that the species recognition behaviour towards same-sex individuals is shifted towards conspecifics with age in interspecifically cross-fostered birds. We conclude that species recognition is irreversible once it has been established in free-living great tits and blue tits. This is the first study to investigate the stability of species recognition in the field.
- Jan 2008
- Encyclopedia of Ecology
Species recognition is often affected by an early learning process called imprinting. The young may learn to recognize their mother and the general characteristics of potential mates and rivals through this learning process. Imprinting further influences many species-typical behaviors through the determination of social preferences and tutor choice. Imprinting is thought to be adaptive because it ensures that a phenotypic change occurring in one generation can be tracked by a social preference for the new phenotype in the next generation, thereby providing some flexibility in response to stochastic events. This learning mechanism may be of great evolutionary significance in processes of speciation and sexual selection.
Imprinting plays a key role in the development of species recognition, with young imprinting upon the morphological characters of their parents. However, the potential role that cultural transmission might play in species recognition remains largely uninvestigated. Great tits (Parus major) and blue tits (Cyanistes caeruleus) do not normally perceive each other as sexual competitors or potential partners. However, after reciprocal interspecific cross-fostering, both species may perceive individuals of the foster species as potential rivals or mates. Although the experience of being raised by heterospecifics clearly has affected the species recognition of cross-fostered birds, some of them breed naturally with conspecifics. The offspring of such cross-fostered birds (OCF) are hence raised by parents that look like ordinary conspecifics but display deviant species recognition as compared to controls in terms of aggressive response towards rivals. Comparing the aggressive behavior of OCF, cross-fostered birds and controls towards territorial intruders may thus help tease apart the influence of morphological vs behavioral cues of parents in the development of offspring species recognition. To this end, we compared birds from all three treatments with respect to their aggressive response to territorial intruders of both species during the breeding season. OCF and controls did not differ in their pattern of response towards heterospecific and conspecific stimuli. Compared to cross-fostered birds, OCF and controls showed less aggression towards heterospecific intruders, while the response towards conspecific intruders did not differ between treatments. These results demonstrate that both tit species imprint on the morphological characters of their parents, but that parental behavior is not important for the development of species recognition in terms of aggressive response towards territorial intruders.
- Jul 2006
Through a cross-fostering experiment, we studied song learning of blue tit, Cyanistes caeruleus, and great tit, Parus major, males reared by heterospecific parents. This was done in the wild, and so potential song tutors, territorial neighbours, potential mates and other social factors were all natural and not affected by the treatment. Normally, the song repertoires of the two species are completely discrete. However, the cross-fostered great tit males altered their song in several aspects, including repertoire size and composition, and temporal and frequency parameters, thus becoming intermediate between the normal songs of the two species. For the cross-fostered blue tit song, only repertoire composition was affected. However, an analysis of repertoire size in both species proved this to be larger in cross-fostered than in control males. This increase in repertoire size shows that repertoire size is influenced by social conditions in these species and is not strictly constrained by memory capacity. Furthermore, several of the cross-fostered great tit males included trilled songs in their repertoires. In these two species, trilled songs have been regarded as unique to the blue tit. In conclusion, our results show the importance of early social experiences for song learning in these wild tits.
Extrapair paternity (EPP) has proved to be widespread and highly variable among birds and other taxa, including socially monogamous species. A multitude of hypotheses have been put forward to explain this variation, but its occurrence is not fully understood. Male age, social dominance rank, song and breeding density or synchrony have been among the suggested correlates of EPP, but results so far are inconclusive. We interspecifically cross-fostered blue tits (Parus caeruleus) and great tits (Parus major) in the wild, thus manipulating males to exhibit reduced social dominance rank, sing aberrant songs, and consequently be perceived as low-quality males as compared to controls. This allowed us to test if male quality had an influence on loss of paternity. We found no statistically significant differences between cross-fostered and control males of either species, neither with respect to levels of cuckoldry nor proportions of extrapair young (EPY) in the broods. Paternity levels were comparable to other studies on the same species. No effect of density could be detected on levels of EPP either, while an age effect seemed to be present at least in the blue tit, EPY being almost absent in broods of older blue tit males. We conclude that the effects of male quality on paternity loss are minor, if any, in these populations. Copyright 2005.
Social dominance influences the outcome of competitive interactions over limited resources, and may hence be important for individual fitness. Theory thus predicts that its heritability will be low and that non-genetic determinants of dominance should prevail. In this field experiment we reciprocally cross-fostered great tits (Parus major) to blue tits (Parus caeruleus) to investigate the impact of early social experience on dominance status in competition over food during winter. Controlling for potential effects of age, size, sex and site-related dominance, we show that cross-fostered birds of both species were subdominant to conspecific immigrants, while controls originating from unmanipulated broods were dominant to conspecific immigrants. Furthermore, blue tits reared by blue tit parents but with at least one great tit broodmate had lower dominance status relative to conspecific immigrants than did controls. Although great tits generally dominated blue tits, cross-fostered birds of both species initiated marginally more fights against the other species than did their respective controls, suggesting faulty species recognition. Since both social parents and broodmates strongly influence the dominance behavior of offspring later in life, we conclude that social conditions experienced at an early age are crucial for the determination of subsequent social dominance. Copyright 2004.
- Jun 2003
Failure to recognize conspecifics in social interactions such as mate choice and aggressive encounters will often result in reduced fitness. Studies on mate choice show that the ability to recognize conspecifics as mates is not universally present at birth, but often needs to be learned. In contrast, little is known about the ontogeny of intrasexual species recognition. To test whether learning influences the recognition of sexual rivals, we compared the aggressive response towards intruders of interspecifically cross-fostered individuals and controls reared by conspecific parents. We simulated territorial intrusion by presenting either a caged individual or playback song near the nest of breeding pairs of great tits, Parus major, and blue tits, P.caeruleus. Great tits reared by blue tit parents responded much more to blue tit stimuli than did great tit controls, and furthermore showed stronger responses to blue tit stimuli than to those of their own species. Blue tits reared by great tits responded much more to great tit stimuli than did blue tit controls. In contrast, blue tits cross-fostered to coal tits, P.ater, did not respond more to coal tits than did blue tit controls. There was a species difference in the response to conspecifics: blue tits cross-fostered to great tits responded more to conspecifics than did cross-fostered great tits. The results were similar for males and females. We conclude that learning influences intrasexual species recognition in these tits. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.
Forord Takk til Tore Slagsvold som ga meg muligheten til å gjennomføre dette arbeidet. Hans erfaring har vaert uvurderlig både i felt og på kontoret. Feltarbeid er en velsignet mulighet for atferdsøkologer. Mange synes det høres romantisk ut å slentre rundt i skogen med kikkert. Sola skinner, hvitveisen blomstrer, og der sitter den aller mest interessante fuglen og gjør akkurat det du hadde håpet den skulle gjøre! Ja, da har jeg det godt! Men livet i felt kan også vaere innmari slitsomt og by på mange skuffelser. Som når du har stått opp en time før sola i mai og ingen av fuglene du hadde planlagt å ta opp sang av vil synge. Kaffe hjelper ikke da. Eller enda verre: røyskatta har krabbet inn i enda en fuglekasse og spist opp alle dataene dine. Tore vet hvordan slike situasjoner skal håndteres. Enten har han en praktisk løsning på problemet, eller så er svaret enkelt, men smertelig: her må det jobbes enda hardere. Han går alltid foran med et godt eksempel og jobber minst like mye som sine doktorander. Samtidig som han alltid er tilgjengelig og har tid til å slå av en prat. Tores kunnskaper og arbeidskapasitet har vaert svaert inspirerende for meg i arbeidet med denne avhandlinga. Takk til Øistein Haugsten Holen og Lars Erik Johannessen for sosialt samvaer både på og utafor universitetet. Deres selskap har vaert svaert viktig. Takk også for nyttige vitenskapelige innspill underveis. Og for hjelp med den dumme, dumme datamaskina.
Sexual-selection theories generally assume that mating preferences are heritable traits. However, there is substantial evidence that the rearing environment may be important for the development of mating preferences, indicating that they may be learnt, or modified by experience. The relative importance of such sexual imprinting across species remains largely unexplored. Here, we report results of a large-scale cross-fostering experiment in the wild in which nestling birds were raised by parents of a different species. We show that resulting sexual imprinting may have a negative effect on pairing success in one species (the great tit, Parus major), but not in two other species (the blue tit, P. caeruleus and the pied flycatcher, Ficedula hypoleuca). A remarkable variation thus seems to exist, even between species that are congeneric and have similar breeding ecologies. The cross-fostering resulted in heterospecific pairings between the two tit species (female blue tit breeding with male great tit), which has never, to our knowledge, been previously documented. However, the chicks fledging from these nests were all blue tit.
- Nov 2001
We discuss two pathways along which obligate brood parasitism (OBP) may evolve and examine some of the critical steps that must be passed by letting great tits Parus major be reared by blue tits Parus caeruleus in a field experiment. The cross-fostered chicks survived well in blue tit nests, but their local recruitment and reproductive success was much lower than that of controls. The effect was strongest when great tits grew up with siblings of the host species rather than with conspecific siblings in blue tit nests. The low success seemed to be caused by misimprinting because the cross-fostered birds behaved like blue tits in several aspects (species association, alarm calls, and aggressive response by resident females to caged intruders). Some birds of both sexes were apparently so strongly imprinted that they did not attract or accept a social mate of their own species. We conclude that imprinting may be necessary for OBP to evolve in birds because the parasite must be attracted to the nests of the host species to add eggs and thereby continue the parasitic life cycle. However, strong imprinting may also prevent OBP from occurring if parasitic offspring seek a mate from the host species.
Fluctuating asymmetry in bilateral traits has been proposed to reflect aspects of individual quality, and has hence been suggested to act as a cue in mate choice. Since sexual selection generally acts more strongly on males, numerous studies have focused on female preferences for symmetrical partners, while very little is known about potential male symmetry preferences. In the present experiment, we tested whether bluethroat males are sensitive to symmetry in an artificial ornament. Using different combinations of blue and orange leg bands, females were made symmetrical or asymmetrical. In outdoor aviaries placed in breeding habitat, males were allowed to choose between a symmetrical and an asymmetrical female. We found that males associated more with symmetrical than asymmetrical females, indicating a preference for symmetry. The magnitude of the symmetry preference of bluethroat males was similar to that of females of the same species.
Males and females have been reported to differ in their feeding of large and small siblings in several species of birds. According to recent hypotheses, this phenomenon may be related to a sexual conflict over avian hatching patterns. We designed an experiment to test for the existence of such a sex difference by manipulating nestling size hierarchies of the bluethroat (Luscinia s. svecica) in two directions; half the broods were “asynchronized” to yield large size-differences within broods and the other half were “synchronized” to yield small size-differences. In all broods, nestlings were categorized as being either large or small according to body mass. We recorded male and female food distribution by video early (day 4 after hatching) and late (day 8) in the nestling period. Males and females did not differ in their distribution of food among different-sized nestlings. With large size-differences, both males and females fed large nestlings nearly twice as often as small ones. In contrast, when the size-differences were small, food was more evenly distributed among nestlings. Early in the nestling period, males fed more nestlings during each feeding visit than did females. Our finding that male and female bluethroats do not differ in the feeding of large and small siblings is in contrast to most previous studies. Variation in costs and benefits to males and females from feeding different-sized nestlings, and restrictions to parental choice due to nestling interactions, may explain interspecific variation.
Female ornaments in animals with conventional sex roles have traditionally been considered non-functional, being merely a genetically correlated response to selection for male ornamentation. Alternatively, female ornaments may be influenced by selection acting directly on the females, either through female–female competition or male choice. We tested the latter hypothesis in mate choice experiments with bluethroats (Luscinia s. svecica), a passerine bird in which females vary considerably in coloration of an ornamental throat patch. In outdoor aviaries placed in prime breeding habitat, males were allowed to choose between a colourful and a drab female. We found that males associated more with, and performed more sexual behaviours towards, colourful females. Female coloration was not age-related, but correlated significantly with body mass and tarsus length. Thus, we have demonstrated both a male preference for female ornamentation, and a relationship between ornament expression and female body size, which may be indicative of quality. Our results refute the correlated response hypothesis and support the hypothesis that female ornamentation is sexually selected.