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Background: Cycling is a popular sport among men. Despite its health benefits, fears have been raised regarding its effects on erectile dysfunction (ED), fertility, and on serum prostate-specific antigen levels. This study aimed to examine associations between regular cycling and urogenital abnormalities in men. Methods: A cross-sectional population study of 5,282 male cyclists was conducted in 2012-2013 as part of the Cycling for Health UK study. The data were analyzed for risk of self-reported ED, physician-diagnosed infertility, and prostate cancer in relation to weekly cycling time, categorized as <3.75, 3.75-5.75, 5.76-8.5, and >8.5 hours/week. Results: There was no association between cycling time and ED or infertility, disputing the existence of a simple causal relationship. However, a graded increase (p-trend=0.025) in the risk of prostate cancer in men aged over 50 years (odds ratios: 2.94, 2.89, and 6.14) was found in relation to cycling 3.75-5.75, 5.76-8.5, and >8.5 hours/week, respectively, compared to cycling <3.75 hours/week. Conclusions: These null associations refute the existence of a simple causal relationship between cycling volume, ED, and infertility. The positive association between prostate cancer and increasing cycling time provides a novel perspective on the etiology of prostate cancer and warrants further investigation.
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... We discuss two large, cross-sectional, observational, surveys of male cyclists. The first by Hollingworth, Harper, and Hamer (2014) reports results deriving from the 2012-13 Cycling for Health UK study which consisted of 5,282 male cyclists. As detailed below, this study claimed a dose-response relationship between amount of cycling per week and prostate cancer risk. ...
... That is, we need to know both the probability of having prostate cancer amongst cyclists, P(prostate|cyclist), and the probability of having prostate cancer in non-cyclists, P(prostate|¬cyclist). We can obtain estimates of P(prostate|cyclist) from observational studies measuring the frequency of prostate cancer in cyclists, such as Hollingworth et al. (2014) and Koupparis et al. (2020). Without direct measurement of the risk of prostate cancer in non-cyclists, we can estimate this by first noting that the overall probability of having prostate cancer, P(prostate) is defined as P(prostate) ! ...
... One of the key characteristics of the datasets from Hollingworth et al. (2014) and Koupparis et al. (2020) is that participants were cyclists. So in interpreting the very low rate of prostate cancer in survey respondents, we must also take possible selection bias into account. ...
Men have a very high lifetime risk of developing prostate cancer, and so there is a pressing need to understand factors that influence this risk. One factor of interest is whether cycling increases of decreases prostate cancer lifetime risk. Two large observational studies of cyclists noted very low rates of prostate cancer amongst cyclists relative to the general population - neither however drew causal conclusions about risk based on this observational prevalence data alone. Here we explore if and how we can use such data to update our beliefs about whether cycling increases or decreases prostate cancer risk - we use probabilistic methods to quantify belief in risk given the observational data available. We examine whether there is a dose-response relationship, how we can make inferences about risks, and the impact upon selection bias upon these inferences. A simple analysis leads us to believe that cycling decreases risk, but we show how this is mistaken unless selection bias can be ruled out. If cyclists who develop prostate cancer are less likely to respond to these surveys, we may be mislead into believing that cycling decreases risk even if it actually increases risk. Overall we explore precisely why it is hard to draw conclusions about risk factors based upon observational prevalence data.
... Of the studies reviewed, 4 were excluded for using non-validated questionnaires (including a single question to assess ED, 16,17 pharmacologic erectile testing, 18 and a questionnaire from the Massachusetts Male Aging Study. 19 ) Of the 6 included studies that used a validated instrument to define ED, 5 used the SHIM score. ...
... Another study including 688 men showed that after controlling for age and ED risk factors such as hypertension, smoking, and diabetes mellitus, increasing time spent in cycling was not significantly associated with ED. 30 Similarly, the largest study to date on the topic including 5,282 men found the same null association, with the additional finding that the strongest predictors of ED were hypertension, smoking, and older age. 16 A history of overt perineal trauma is an important risk factor for vasculogenic ED yet was not consistently characterized among the studies in the present analysis. In cyclists, this most commonly occurs from falling forward onto the top tube of the bicycle frame. ...
Conflicting evidence exists on the relationship between bicycle riding and erectile dysfunction (ED). A major limitation to several prior studies is the lack of a validated measure of ED.
To assess the relationship between cycling and clinically validated ED based on existing literature.
We searched several major databases from database inception through 2018 using a variety of search terms relating to “cycling” and “erectile dysfunction.” Studies were included if they were written in English, reported original data, compared ED between cyclists and non-cycling controls, and used a validated measure of ED, such as the International Index of Erectile Function or the subset Sexual Health Inventory for Men (SHIM). Age, SHIM score, and comorbidities were extracted for all groups. Primary outcomes for each group were mean SHIM score and presence of ED (SHIM ≤ 21). A generalized linear mixed-effects model was used to fit the collected data for meta-analysis. Main outcome measures were unadjusted odds ratios of ED for cyclists and non-cyclists, mean SHIM score difference between cyclists and noncyclists, and both of these measures adjusted for age and comorbidities.
After a systematic evaluation of 843 studies, 6 studies met our inclusion criteria, encompassing 3,330 cyclists and 1,524 non-cycling controls. When comparing cyclists to non-cyclists in an unadjusted analysis, there were no significant differences in the odds of having ED or mean SHIM score. However, when controlling for age and comorbidities, cyclists had significantly higher odds of having ED (odds ratio: 2.00; 95% confidence interval: 1.57, 2.55).
Limited evidence supports a positive correlation between cycling and ED when adjusting for age and several comorbidities. Heterogeneity among studies suggests that further investigation into certain populations of cyclists that may be more vulnerable to ED may be beneficial.
Gan ZS, Ehlers ME, Lin FC, et al. Systematic Review and Meta-Analysis of Cycling and Erectile Dysfunction. Sex Med 2020;XX:XXX–XXX.
... Although cycling improves health in the cyclist and the general public (reduced pollution), there may be negative 4 3 health effects. A study on WBV disproved that cycling increases the risk of reproductive issues in men but suggested a possible link with prostate cancer . Short-term vibration through the hands may reduce grip strength and circulation . ...
... It is not used in any reviewed literature for HAV making it unusable for comparative purposes. CoVWR uses the below equations to define the terms a hv and A (8). A(8) includes time consideration, but a hv does not. ...
Concerns exist in the cycling community and in relevant literature that cycling-induced, hand-arm vibration in urban environments could amount to unsafe or unduly uncomfortable levels. Published studies focus on controlled, unrepresentative samples or unusually rough surfaces. This research aims to provide vibration exposure information specific to and representative of urban bicycle commuters. A programme of triaxial vibration levels and vibration exposure measurements was undertaken on a representative rigid bicycle for different conditions at the handlebar. A varied and representative sample of London (UK) roads used for commuting was employed. The effect of front shock absorbers was studied. Results were assessed against safe and comfortable levels of vibration found in relevant guidance and in occupational regulations. It was found that cycling on typical urban roads and cycle routes does not expose riders to unsafe levels of hand-arm vibration. However values reached levels of discomfort potentially leading to early fatigue and discomfort. The different effectiveness of traditional suspension and novel suspension in the stem was determined and their virtues compared.
... Authors from University College London conducted a large cross-sectional study providing a snapshot view of cycling habits and prostate cancer diagnoses from a sample of the population. 1 The study was not focused on prostate cancer alone. The authors hypothesised an association between weekly cycling 'volume' and genitourinary problems including erectile dysfunction (ED), infertility and prostate cancer on the basis of repetitive trauma to the perineum leading to recurrent inflammation and compression of anatomical structures. ...
Alastair Lamb discusses a recent study that suggested a link between cycling and prostate cancer, and asks whether the evidence stacks up.
... Cycling has long been associated with erectile dysfunction and infertility , although two recent large survey-based studies did not demonstrate such associations [14,15]. Nevertheless, multiple smaller studies have linked cycling to impaired semen parameters. ...
Many common sports and sports-related behaviors and practices represent potential sources of male infertility. Clinicians should be aware of these associations in the evaluation of idiopathic infertility in men.
... The observation that the type and duration of sport activities may influence the occurrence of prostate carcinoma (as well as erectile dysfunction and infertility) makes interpretation of AASs abuse even more difficult. In cyclists over 50 years of age, a clear positive correlation between the incidence of prostate cancer and hours of weekly cycling time (!3.75 vs O8.5 h/week) was found (50). Furthermore, the observation that hypogonadal men treated with therapeutic doses of testosterone do not suffer from a higher incidence of prostate carcinoma than patients not treated with testosterone (51) supports the hypothesis that prostate carcinoma develops independently of possible androgen treatment. ...
Anabolic androgenic steroids (AAS) are the favoured appearance and performance enhancing drugs (APED) used in competitive athletics, by body-builders and in recreational sports. Many AAS, often obtained from the internet and dubious sources, have not undergone proper testing and are consumed at extremely high doses and in irrational combinations, also with other drugs. Controlled clinical trials investigating undesired side-effects of AAS are lacking since ethical restrictions prevent exposing volunteers to potentially toxic regimens, thus making it difficult to establish a causal relationship between AAS abuse and possible sequelae. Because of the negative feedback in the regulation of the hypothalamic-pituitary-gonadal axis, in men AAS cause reversible suppression of spermatogenesis, testicular atrophy, infertility and erectile dysfunction (anabolic steroid induced hypogonadism). Should spermatogenesis not recover after AAS abuse, a pre-existing fertility disorder may have resurfaced. AAS frequently cause gynecomastia and acne. In women, AAS may disrupt ovarian function. But as chronic strenuous physical activity leads to menstrual irregularities and, in severe cases, to the female athlete triad (low energy intake, menstrual disorders and low bone mass), it is difficult to disentangle effects of sports and AAS. Acne, hirsutism and (irreversible) deepening of the voice are further consequences of AAS misuse. There is no evidence that AAS cause breast carcinoma. Detecting AAS misuse through the control network of the World Anti-Doping Agency (WADA) not only aims to guarantee fair conditions for the athletes, but also to protect them from medical sequelae of AAS abuse.
... Typically, impacts of active travel (cycling and walking) and inactive travel (traveling by car, bus or train) on health are compared . Although earlier studies offer much evidence on the health benefits of cycling or walking due to increased physical activity , some other studies reveal cycling also carries some potential health risks, including air pollution, accidents and noise . One of the most important risks is from poor air quality [29,30]. ...
With the development of information and communications technology, user-generated content and crowdsourced data are playing a large role in studies of transport and public health. Recently, Strava, a popular website and mobile app dedicated to tracking athletic activity (cycling and running), began offering a data service called Strava Metro, designed to help transportation researchers and urban planners to improve infrastructure for cyclists and pedestrians. Strava Metro data has the potential to promote studies of cycling and health by indicating where commuting and non-commuting cycling activities are at a large spatial scale (street level and intersection level). The assessment of spatially varying effects of air pollution during active travel (cycling or walking) might benefit from Strava Metro data, as a variation in air pollution levels within a city would be expected. In this paper, to explore the potential of Strava Metro data in research of active travel and health, we investigate spatial patterns of non-commuting cycling activities and associations between cycling purpose (commuting and non-commuting) and air pollution exposure at a large scale. Additionally, we attempt to estimate the number of non-commuting cycling trips according to environmental characteristics that may help identify cycling behavior. Researchers who are undertaking studies relating to cycling purpose could benefit from this approach in their use of cycling trip data sets that lack trip purpose. We use the Strava Metro Nodes data from Glasgow, United Kingdom in an empirical study. Empirical results reveal some findings that (1) when compared with commuting cycling activities, non-commuting cycling activities are more likely to be located in outskirts of the city; (2) spatially speaking, cyclists riding for recreation and other purposes are more likely to be exposed to relatively low levels of air pollution than cyclists riding for commuting; and (3) the method for estimating of the number of non-commuting cycling activities works well in this study. The results highlight: (1) a need for policymakers to consider how to improve cycling infrastructure and road safety in outskirts of cities; and (2) a possible way of estimating the number of non-commuting cycling activities when the trip purpose of cycling data is unknown.
... Through enhancing physical activity, active travel (cycling or walking) produces health benefit (Forsyth et al., 2012;Oja et al., 1998Oja et al., , 2011Pucher et al., 2010;Wen and Rissel, 2008). At the same time, as outdoor physical activities cycling and walking are also of risks, including traffic accidents and air pollution exposure (Weichenthal et al., 2011;de Nazelle et al., 2013;Hollingworth et al., 2014). Generally speaking, recent studies support both empirically and theoretically that the total benefits of active travel tend to outweigh the risks (Tainio et al., 2016;Doorley et al., 2015;Mueller et al., 2015). ...
Improvement on assessment of air pollution exposure will enhance assessment of health risk-benefit when active travel (cycling and walking). Earlier studies assessed air pollution exposure according to travel time and city-level air pollution. The lack of spatially fine-grained travel data is a barrier to an accurate assessment of air pollution exposure. Due to a high-level spatial granularity, Strava Metro provides an opportunity to assessing air pollution exposure in combination with spatially varying air pollution concentrations. Strava Metro anonymized and aggregated a large volume of users’ traces to streets for each city. In this study, to explore the potential of crowdsourced geographic information in research of active travel and health, we used Strava Metro data and GIS technologies to assess air pollution exposure in Glasgow, UK. Particularly, we incorporated time of the trip to assess average inhaled dose of pollutant during a single cycling or pedestrian trip. Empirical results demonstrate that Strava Metro data provides an opportunity to an assessment of average air pollution exposure during active travel. Additionally, to demonstrate the potential of Strava Metro data in policy-making, we explored the spatial association of air pollution concentration and active travel. As a result, we identified areas that require investment priority, and finally offered implications for policies.
... 24 The largest cross-sectional Internet based survey study performed to date was the Cycling for Health UK Study. 25 It included 5,282 cyclists and revealed no statistically significant association between cycling time and ED. Significant limitations in the previous studies were the use of nonvalidated questions, the lack of comparison groups and/or small sample sizes. ...
To explore the relation between cycling and urinary and sexual function in a large, multinational sample of men.
Materials and methods:
Cyclists were recruited to complete a survey through Facebook advertisements and outreach to sporting clubs. Swimmers and runners were recruited as a comparison group. Cyclists were categorized into low and high intensity cyclists. Participants were queried using validated questionnaires, including the Sexual Health Inventory for Men (SHIM), International Prostate Symptom Score (I-PSS), and National Institute of Health Chronic Prostatitis Symptom Index (NIH-CPSI), in addition to questions about urinary tract infections (UTIs), urethral strictures, genital numbness, and saddle sores.
Of 5,488 complete survey responses, 3,932 (72%) were included in our analysis. In a multivariate analysis, swimmers/runners had a lower mean SHIM score compared to low and high intensity cyclists (19.5 vs. 19.9, p=0.02 and 20.7, p<0.001), respectively. No significant differences were found in I-PSS, NIH-CPSI scores, and UTI history. Cyclists had statistically higher odds of urethral strictures compared to swimmers/runners (Odds Ratio (OR) 2.5, p=0.042). Standing more than 20% of the time while cycling significantly reduced the odds of genital numbness (OR 0.4, p=0.006). Adjusting the handlebar higher or even with the saddle had lower odds of genital numbness and saddle sores (OR 0.8, p=0.005, and OR 0.6, p<0.001), respectively.
Cyclists had no worse sexual or urinary functions than swimmers/runners, but cyclists were more prone to urethral strictures. Increased time standing while cycling, and higher handlebar height were associated with lower odds of genital sores and numbness.
... Multiple reports have described ED following cycling activities . However, many recent studies have failed to find associations between moderate cycling and ED after controlling for other variables such as age and comorbidities [33,34]. In a large cross-sectional survey, Marceau et al  seem to isolate the association of ED and cycling to sports cyclists (cycling more than 3 h/wk) and show a protective effect of cycling on ED in moderate cyclists (cycling less than 3 h/wk). ...
Male factor infertility plays a significant role in infertility. Many factors have been associated with male infertility; however, the link between many sports and recreational factors and male reproduction remains poorly characterized.
To evaluate the current literature regarding the impact of many common sports and recreational factors on male reproduction.
A comprehensive PubMed and Embase search for relevant articles published between 1970 and 2017 was performed by combining the following search terms: male, sports (including individual sports), traumatic brain injury, sauna, hot tub, fertility, erectile dysfunction, varicocele, environment, cell phone, and laptop computer.
Hypogonadism and erectile dysfunction can be associated with sports with high rates of head injuries, such as American football. Although early reports linked other sports, such as bicycling, to erectile dysfunction, subsequent studies isolated these associations to sports cycling rather than recreational cycling. Certain sports (football, basketball, handball, and volleyball) were linked to increasing prevalence and severity of varicocele, offering a potential link to male infertility. In addition, recreational activities such as sauna, hot tubs, Jacuzzis, heated car seats, and laptop use were associated with high testicular temperature, which can impair spermatogenesis. Radio frequency electromagnetic waves from cell phones and laptops have also been shown to have deleterious effects on sperm viability and motility.
Many common sports and daily activities represent potential sources of male infertility. Clinicians should be aware of these associations in explaining idiopathic infertility in males.
Male infertility is an often overlooked component of a couple's inability to conceive. We outline many common and often overlooked sports and recreational exposures that have been associated with male infertility.
... evidence that cycling increases the risk of ED in men. 27,28 On the other hand, these findings were not replicable in subsequent studies, 16,29,30 and cycling may be more closely associated with genital numbness. 31 Future research should investigate the net effect of cardiovascular benefits for cyclists, who also experience prolonged perineal compression as they increase exercise duration. ...
Sexual dysfunction is common among adults and takes a toll on quality of life for both men and women.
To determine whether higher levels of weekly cardiovascular exercise are protective against self-reported sexual dysfunction among men and women.
We conducted an international online, cross-sectional survey of physically active men and women between April and December 2016, assessing exercise activity categorized into sextiles of weekly metabolic equivalent-hours. Odds ratios (ORs) of sexual dysfunction for each activity sextile compared with the lowest sextile were calculated using multivariable logistic regression, controlling for age, body mass index, diabetes mellitus, tobacco/alcohol use, sport, and marital status.
Main outcome measures:
Female sexual dysfunction was defined as a score ≤26.55 on the Female Sexual Function Inventory and erectile dysfunction (ED) was defined as a score ≤21 on the Sexual Health Inventory for Men.
3,906 men and 2,264 women (median age 41-45 and 31-35 years, respectively) met the inclusion criteria for the study. Men in sextiles 2-6 had reduced odds of ED compared with the reference sextile in adjusted analysis (Ptrend = .03), with an OR of 0.77 (95% CI = 0.61-0.97) for sextile 4 and 0.78 (95% CI = 0.62-0.99) for sextile 6, both statistically significant. Women in higher sextiles had a reduced adjusted OR of female sexual dysfunction (Ptrend = .02), which was significant in sextile 4 (OR = 0.70; 95% CI = 0.51-0.96). A similar pattern held true for orgasm dissatisfaction (Ptrend < .01) and arousal difficulty (Ptrend < .01) among women, with sextiles 4-6 reaching statistical significance in both.
Men and women at risk for sexual dysfunction regardless of physical activity level may benefit by exercising more rigorously.
Strengths & limitations:
Strengths include using a large international sample of participants with a wide range of physical activity levels. Limitations include the cross-sectional design, and results should be interpreted in context of the study population of physically active adults.
Higher cardiovascular exercise levels in physically active adults are inversely associated with ED by self-report in men and protective against female sexual dysfunction in women. Fergus KB, Gaither TW, Baradaran N, et al. Exercise Improves Self-Reported Sexual Function Among Physically Active Adults. J Sex Med 2019;16:1236-1245.
Cycling is a popular means of transport and recreational activity; bicycles are also a source of genitourinary injuries and there is the idea that cycling may have a significant impact on sexual function. The objective of this study was to evaluate the effect of amateur cycling on erectile function.
We used a questionnaire comparing amateur cyclists (n = 199) and footballers (n = 43), regarding sexual related comorbidities and hours of practice per week. The cyclists were also characterized in terms of road vs cross-country, breaks during cycling, saddle, and shorts. To evaluate erectile function, the International Index of Erectile Function questionnaire was applied.
there was no difference in International Index of Erectile Function total score between groups. Age and presence of erectile dysfunction associated comorbidity were negative factors in the International Index of Erectile Function score in cyclists but not in the footballers.
Cycling is usually associated with perineal numbness, but that numbness did not lead to lower International Index of Erectile Function scores. In conclusion amateur cycling has no effect on EF.
Erectile dysfunction is a common, but treatable, condition. Where appropriate, modification of lifestyle factors, medication optimisation and oral pharmacotherapies can be initiated in primary care. Early recognition and management will improve the quality of life of affected individuals and partners, and may avert relationship problems, negative body image and poor mental health. Erectile dysfunction is also an important early warning sign for conditions such as cardiovascular disease. This article considers the aetiology and risk factors for erectile dysfunction, identifies common clinical features, outlines primary care assessment and treatment, and discusses referral criteria. Treatment options available in secondary care are also reviewed.
This study aimed to examine the association between cycling and men’s health issues, including prostate cancer (CaP), erectile dysfunction (ED), chronic pelvic pain syndrome (CPPS) and lower urinary tract symptoms (LUTs).
Information regarding CaP, ED, CPPS and LUTs were collected from 8074 male cyclists via a unique online men’s health and cycling video produced in conjunction with the Global Cycling Network (GCN) using validated questionnaires. Logistic regression analyses were used to evaluate any relationship between cycling and men’s health issues, including the effect of risk factors.
The GCN video received 619,105 views, and completed data were collected on 8074 male cyclists. Of these, 0.57% had a diagnosis of CaP, 14.5% described ED, 8.82 reported symptoms of CPPS and 12.5% reported LUTs. All reported symptoms were mild, and no correlation was found between cycling and CaP or ED on statistical analyses.
This is the largest worldwide cross-section observational study on the association between cycling and men’s health. It demonstrates no negative association between cycling and CaP, ED, CPPS or LUTs.
Level of evidence
Not applicable for this multicentre audit.
Male infertility is a common medical condition affecting roughly one in ten men and resulting in significant psychological, financial, and overall health consequences for young men, their families, and the healthcare system. The condition is often idiopathic but can also be associated with other comorbidities including unrecognized malignancies, occult genetic conditions, and general health status. Proper diagnosis and management hinges upon a thorough history and physical, timely referral to male infertility specialists, appropriate laboratory workup, and medical or surgical therapy when indicated. In this chapter, we discuss the guideline-based general categorization and workup of male infertility, with an emphasis on identifying underlying comorbidities and causes and a brief introduction of treatment options.KeywordsMale infertilityAzoospermiaVaricoceleOligozoospermiaSurgical sperm retrieval
The last few decades have seen a marked increase in mean life expectancy in Central Europe. This has made elderly people and their quality of life a matter of ever-increasing medical concern. Available data from the United States and Scandinavia relating to erectile dysfunction (ED) do not enable us to draw valid conclusions about the current situation in Germany. The aim of the present study was to evaluate the epidemiology of male sexuality in Germany, and the proportion of men who need medical treatment because of increased suffering from this.A newly developed and validated questionnaire on male erectile dysfunction was mailed to a representative population sample of 8000 men, 30-80 y of age in the Cologne urban district. The response included 4489 evaluable replies (56.1%). The response rates in different age groups ranged from 49.2% to 68.4%. Regular sexual activity was reported by 96.0% (youngest age group) to 71.3% (oldest group). There were 31.5%-44% of responders who were dissatisfied with their current sex life. The prevalence of ED was 19.2%, with a steep age-related increase (2.3-53.4%) and a high co-morbidity of ED with hypertension, diabetes, pelvic surgery and 'lower urinary tract symptoms'. When treatment need was defined by co-occurrence of ED and dissatisfaction with sex life, 6.9% men required treatment for ED. Oral treatment of ED was preferred by 73.8% of respondents. There were 46.2% respondents who were willing to contribute more than DM 50 (25 Euro) per month for ED treatment. We conclude that regular sexual activity is a normal finding in advanced age. ED is a frequent disorder, contributing to dissatisfaction with sex life in a considerable proportion of men. The high burden of ED is reflected in willingness to pay for treatment. ED is frequently associated with chronic diseases. Therefore adequate diagnostic workup is essential, to offer patients individually adapted treatment. General non-reimbursability of treatment for ED appears to be unacceptable.
An association between bicycling and erectile dysfunction (ED) has been described previously, but there are limited data examining this association in a random population of men. Such data would incorporate bicyclists with varied types of riding and other factors. Data from the Massachusetts Male Aging Study (MMAS) were utilized to examine the association between bicycling and ED. Logistic regression was used to test for an association, controlling for age, energy expenditure, smoking, depression and chronic illness. Bicycling less than 3 h per week was not associated with ED and may be somewhat protective. Bicycling 3 h or more per week may be associated with ED. Data revealed that there may be a reduced probability of ED in those who ride less than 3 h per week and ED may be more likely in bikers who ride more than 3 h per week. More population-based research is needed to better define this relationship.
The authors assessed the accuracy of cause(s) of subfertility as reported by women in a self-administered questionnaire in comparison with medical record information, in a nationwide cohort study of women receiving in vitro fertilization treatment in the Netherlands (n = 9,164) between 1983 and 1995. Validity was expressed as sensitivity and specificity, and reliability was expressed by the kappa statistic and overall agreement between self-reports and medical records for various subfertility categories. The sensitivity for subfertility attributed to tubal, male, hormonal, cervical, uterine, and idiopathic factors and for endometriosis was 84%, 78%, 65%, 40%, 46%, 59%, and 83%, respectively. The corresponding kappas were 0.79, 0.71, 0.38, 0.34, 0.13, 0.50, and 0.52, respectively. For 54% of all women who reported two or more causes of subfertility, the medical record revealed only one major factor. Conversely, for 43% of all women whose subfertility was attributed to two or more major factors in the record, only one factor was reported by the women. Older age at the time of filling out the questionnaire, low educational level, long duration of subfertility, and pre-in vitro fertilization treatment were associated with less accurate reporting. The results indicate that the validity of self-reports for tubal and male subfertility is satisfactory. For unexplained subfertility, the validity is moderate; for other causes of subfertility and when two causes of subfertility play a role, the validity is low.
Bradford Hill's considerations published in 1965 had an enormous influence on attempts to separate causal from non-causal explanations of observed associations. These considerations were often applied as a checklist of criteria, although they were by no means intended to be used in this way by Hill himself. Hill, however, avoided defining explicitly what he meant by "causal effect".
This paper provides a fresh point of view on Hill's considerations from the perspective of counterfactual causality. I argue that counterfactual arguments strongly contribute to the question of when to apply the Hill considerations. Some of the considerations, however, involve many counterfactuals in a broader causal system, and their heuristic value decreases as the complexity of a system increases; the danger of misapplying them can be high. The impacts of these insights for study design and data analysis are discussed. The key analysis tool to assess the applicability of Hill's considerations is multiple bias modelling (Bayesian methods and Monte Carlo sensitivity analysis); these methods should be used much more frequently.
To evaluate the blood supply to the penis during bicycling and thus determine whether the associated perineal compression might be responsible for some cases of impotence.
The transcutaneous penile oxygen partial pressure (pO2 ) at the glans of the penis was measured in 25 healthy athletic men; pO2 is readily measured by noninvasive techniques currently widely used in the management of premature infants, and which have been shown to give pO2 levels that correlate with arterial pO2 levels. The measurements in the healthy subjects were taken in various positions, before, during and after bicycling.
The mean (sd) pO2 of the glans when standing before cycling was 61.4 (7.2) mmHg; it decreased after 3 min of cycling to 19.4 (4. 7) mmHg. After 1 min of cycling in a standing position it increased significantly to 68 (7.6) mmHg; when cycling was continued in a seated position, after 3 min the pO2 fell to 18.4 (4.2) mmHg and there was a full return to normal pO2 values after a 10-min recovery period.
The pO2 seems to correlate with the blood supply to the penis. The present results support the hypothesis that as the penile arteries are compressed against the pubic bone by the saddle during bicycling, the pO2 values decrease. Additionally, shifting from a seated to a standing position while cycling significantly improved the pO2 value of the penis and penile blood oxygenation was then even greater. Therefore, we suggest that cyclists change their body position frequently during cycling. Correcting the handlebars or the height of the saddle, tipping the nose of the saddle to produce a more horizontal, or even downward pointing position, and attention to the design of the saddle may be the only required precautions.
To determine how well a single question of self-reported erectile dysfunction compares to a gold standard clinical urologic examination.
Clinical validation study nested within the Massachusetts Male Aging Study (MMAS), which is an observational cohort study of aging and health in a population-based random sample of men.
During an in-person interview, men were asked to respond to a single-question self-report of erectile dysfunction. A subsample of MMAS participants was then subjected to a clinical urologic examination to obtain a clinical diagnosis of erectile dysfunction.
One hundred thirty-nine men 55 to 85 years of age from the MMAS.
Complete data were available from 137 men. Erectile dysfunction (ED) measured by self-report and independent urologic examination were strongly correlated (Spearman r=.80). Receiver operating curve analysis showed that the self-reported ED item accurately predicts the clinician-diagnosed ED (area under the curve [AUC]=0.888). Stratum-specific likelihood ratios (95% confidence intervals) for self-reports predicting the gold standard were: no ED=0.11 (0.06 to 0.22), minimal ED=1.48 (0.67 to 3.26), moderate ED=8.57 (1.21 to 60.65), and complete ED=12.69 (1.81 to 88.79). These data indicate that men diagnosed with ED by urologic examination can be distinguished from men not diagnosed with ED by urologic examination if the respondent self-reported no, moderate, or complete ED.
Our single-question self-report accurately identifies men with clinically diagnosed ED, and may be useful as a referral screening tool in both research studies and general practice settings.