Bo V Pedersen

Statens Serum Institut, Copenhagen, Capital Region, Denmark

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Publications (26)153.48 Total impact

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    ABSTRACT: Current knowledge concerning the association between exposure to stressful life-events (SFLEs) in childhood and later risk of multiple sclerosis (MS) is sparse. We studied the associations between SFLEs in childhood and subsequent risk of MS in a nationwide cohort of 2.9 million Danes born from 1968 to 2011. A SFLE in childhood was defined as exposure before age 18 years to parental divorce, parental death, or death of a sibling, using information from the Danish Civil Registration System. MS cases in the cohort were identified in the Danish Multiple Sclerosis Registry. Associations of SFLE with MS risk were evaluated by incidence rate ratios (RR) of MS obtained in log-linear Poisson regression models. Persons exposed to any SFLE in childhood were at 11% elevated risk of MS (RR = 1.11; 95% confidence interval: 1.03-1.20), compared to non-exposed persons. Stratification by subtype of SFLE showed that parental death and death of a sibling were not associated with MS risk. However, persons exposed to parental divorce were at 13% increased risk of developing MS compared to non-exposed (RR = 1.13; 1.04-1.23). Associations of SFLEs in childhood with risk of MS are weak. However, parental divorce is somehow associated with modestly increased risk of MS.
    Multiple Sclerosis 03/2014; · 4.47 Impact Factor
  • Morten Frisch, Nete Munk Nielsen, Bo Vestergaard Pedersen
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    ABSTRACT: Autoimmune diseases have been little studied in gay men and lesbians. We followed 4.4 million Danes, including 9,615 same-sex married (SSM) persons, for 47 autoimmune diseases in the National Patient Registry between 1989 and 2008. Poisson regression analyses provided first hospitalization rate ratios (RRs) comparing rates between SSM individuals and persons in other marital status categories. SSM individuals experienced no unusual overall risk of autoimmune diseases. However, the risk of autoimmune thyroid dysfunction was increased, notably Hashimoto's thyroiditis (womenSSM, RR = 2.92; 95 % confidence interval (CI) 1.74-4.55) and Graves' disease (menSSM, RR = 1.88; 95 % CI 1.08-3.01). There was also an excess of primary biliary cirrhosis (womenSSM, RR = 4.09; 95 % CI 1.01-10.7), and of psoriasis (menSSM, RR = 2.48; 95 % CI 1.77-3.36), rheumatic fever (menSSM, RR = 7.55; 95 % CI 1.87-19.8), myasthenia gravis (menSSM, RR = 5.51; 95 % CI 1.36-14.4), localized scleroderma (menSSM, RR = 7.16; 95 % CI 1.18-22.6) and pemphigoid (menSSM, RR = 6.56; 95 % CI 1.08-20.6), while Dupuytren's contracture was reduced (menSSM, RR = 0.64; 95 % CI 0.39-0.99). The excess of psoriasis was restricted to same-sex married men with HIV/AIDS (menSSM, RR = 10.5; 95 % CI 6.44-15.9), whereas Graves' disease occurred in excess only among same-sex married men without HIV/AIDS (menSSM, RR = 1.99; 95 % CI 1.12-3.22). Lesbians and immunologically competent gay men in same-sex marriage face no unusual overall risk of autoimmune diseases. However, the observed increased risk of thyroid dysfunction in these lesbians and gay men deserves further study.
    European Journal of Epidemiology 12/2013; · 5.12 Impact Factor
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    ABSTRACT: In a national cohort comprising 1.5 million Danes born from 1966 to 1992, we studied the association between childhood socioeconomic status (SES) and the risk of multiple sclerosis (MS) from 1981 to 2007 using information about household income and parental educational levels at the person's 15th birthday. The association between childhood SES and MS was evaluated using MS incidence rate ratios with 95% confidence intervals obtained in log-linear Poisson regression analyses. We found no strong association between childhood SES and MS but did observe a tendency toward a reduced risk of MS among children from households with more highly educated parents, particularly mothers. Children whose mothers had a secondary (rate ratio = 0.95, 95% confidence interval: 0.86, 1.04) or higher (rate ratio = 0.86, 95% confidence interval: 0.76, 0.97) education had reduced risks of MS (5% and 14%, respectively) compared with children of mothers with a basic education (P for trend = 0.02). Results were practically unchanged in an analysis restricted to persons aged 15-29 years, among whom the possible effect of own SES on MS risk is considered limited. Overall, SES in childhood seems of no major importance for the subsequent risk of MS; however, offspring of well-educated mothers may be at a slightly reduced risk of MS.
    American journal of epidemiology 05/2013; · 5.59 Impact Factor
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    ABSTRACT: BACKGROUND: Apart from a recent study reporting a 2- to 3-fold increased risk of multiple sclerosis (MS) among women and men who were delivered by Cesarean section (C-section), little attention has been given to the possible association between mode of delivery and the risk of MS. OBJECTIVES: We studied the association between C-section and risk of MS, in a cohort of 1.7 million Danes born from 1973 to 2005. METHODS: Information on C-section and MS was obtained from the Danish Medical Birth Register and the Danish MS Register, respectively. The association between C-section and MS was evaluated by means of MS incidence rate ratios (RR) with 95% confidence intervals (CI) obtained in log-linear Poisson regression analyses. RESULTS: There were 930 cases of MS in the study cohort, of whom 80 (9%) were delivered by C-section. Overall, we found there was no significant association between C-section and risk of MS (RR = 1.17; 0.92-1.46). Analyses stratified by sex revealed no unusual risk of MS for women (RR = 1.08: 0.80-1.42) nor men (RR = 1.37: 0.91-1.98). A supplementary sibling-matched Cox regression analysis likewise suggested there was no excess risk of MS in persons delivered by C-section (HR = 1.03; 0.63-1.69). CONCLUSIONS: Mode of delivery appears to be unimportant in relation to MS development in the offspring.
    Multiple Sclerosis 03/2013; · 4.47 Impact Factor
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    ABSTRACT: The risk for colorectal cancer (CRC) in patients with inflammatory bowel disease (IBD) could have changed over time, with changes in treatment options. We studied CRC risk in a nationwide cohort of 47,374 Danish patients with IBD over a 30-year period. We determined relative risk (RR) values using Poisson regression-derived incidence rate ratios of CRC from 1 year after IBD diagnosis, adjusted for age, sex, and calendar time. We compared incidence of CRC among patients with IBD vs individuals without IBD. During 178 million person-years of follow-up evaluation, 268 patients with ulcerative colitis (UC) and 70 patients with Crohn's disease (CD) developed CRC. The overall risk of CRC among patients with UC was comparable with that of the general population (RR, 1.07; 95% confidence interval [CI], 0.95-1.21). However, patients diagnosed with UC in childhood or as adolescents, those with long duration of disease, and those with concomitant primary sclerosing cholangitis were at increased risk. For patients with UC, the overall RR for CRC decreased from 1.34 (95% CI, 1.13-1.58) in 1979-1988 to 0.57 (95% CI, 0.41-0.80) in 1999-2008. Among patients with CD, the overall RR for CRC was 0.85 (95% CI, 0.67-1.07), which did not change over time. A diagnosis of UC or CD no longer seems to increase patients' risk of CRC, although subgroups of patients with UC remain at increased risk. The decreasing risk for CRC from 1979 to 2008 might result from improved therapies for patients with IBD.
    Gastroenterology 04/2012; 143(2):375-81.e1; quiz e13-4. · 12.82 Impact Factor
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    ABSTRACT: The risk of some female predominant autoimmune diseases (ADs) has previously been shown to be higher in women who experience hyperemesis, gestational hypertensive disorders and idiopathic pregnancy losses. This study assessed the association between such pregnancy-related experiences and the subsequent risk of female predominant and other ADs. Our study cohort comprised 1.6 million Danish women born since 1955 for whom we had information about hyperemesis, gestational hypertensive disorders and pregnancy losses and subsequent hospital contacts for 31 ADs between 1982 and 2008. Ratios of first hospitalization rates (RRs) with 95% confidence intervals (CIs) were calculated using Poisson regression, adjusting for age, birth cohort, calendar period, marital status and childbirths. During 27.0 million person-years of follow-up 51,732 women were hospitalized with one or more ADs. Overall, compared with women without the specific pregnancy experiences, the risk of any AD was significantly increased for women with hyperemesis (RR = 1.41; 95% CI 1.30-1.51), gestational hypertensive disorders (1.21; 1.16-1.26), spontaneous abortions (1.10; 1.07-1.14), missed abortions (1.09; 1.04-1.13), stillbirths (1.25; 1.12-1.40), ectopic pregnancies (1.08; 1.02-1.14) and induced abortions (1.07; 1.04-1.09). Associations with female predominant ADs (i.e., ADs with a female:male ratio >2:1) were strongest in the first five years after the studied pregnancy experiences, but overall there was little difference between the RRs for groups of female predominant ADs and other ADs. Strong and potentially biological associations were observed for a number of specific ADs; including systemic lupus erythematosus, Graves' disease, type 1 diabetes mellitus and pernicious anemia, and for some specific ADs associations persisted even more than five years after the abnormal pregnancy experience. Abnormal pregnancies are associated with increased risk of certain ADs, possibly because of underlying immunologic or hormonal factors that predispose to both adverse pregnancy experiences and AD development.
    Journal of Autoimmunity 01/2012; 38(2-3):J120-8. · 8.15 Impact Factor
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    ABSTRACT: An association between endometriosis and certain autoimmune diseases has been suggested. However, the impact of endometriosis on risk of inflammatory bowel disease (IBD) remains unknown. To assess the risk of Crohn's disease (CD) and ulcerative colitis (UC) in an unselected nationwide Danish cohort of women with endometriosis. By use of national registers, 37 661 women hospitalised with endometriosis during 1977-2007 were identified. The relative risk of developing IBD after an endometriosis diagnosis was calculated as observed versus expected numbers and presented as standardised incidence ratios (SIRs) with 95% CIs. Women with endometriosis had a increased risk of IBD overall (SIR=1.5; 95% CI 1.4 to 1.7) and of UC (SIR=1.5; 95% CI 1.3 to 1.7) and CD (SIR=1.6; 95% CI 1.3 to 2.0) separately, even 20 years after a diagnosis of endometriosis (UC: SIR=1.5; 95% CI 1.1 to 2.1; CD: SIR=1.8; 95% CI 1.1 to 3.2). Restricting analyses to women with surgically verified endometriosis suggested even stronger associations (UC: SIR=1.8; 95% CI 1.4 to 2.3; CD: SIR=1.7; 95% CI 1.2 to 2.5). The risk of IBD in women with endometriosis was increased even in the long term, hence suggesting a genuine association between the diseases, which may either reflect common immunological features or an impact of endometriosis treatment with oral contraceptives on risk of IBD.
    Gut 12/2011; 61(9):1279-83. · 10.73 Impact Factor
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    ABSTRACT: To evaluate the possible biological role of pregnancy on the risk of autoimmune diseases we assessed associations between reproductive history and subsequent risk of autoimmune diseases characterized by female predominance and other autoimmune diseases. Our study cohort comprised 4.6 million Danes born since 1935 for whom a complete record of childbirths was available. Cohort members were followed for hospital contacts for 31 autoimmune diseases from 1982 to 2008. Female predominant autoimmune diseases were those with a female:male sex ratio >2:1. Ratios of first hospitalization rates were calculated using Poisson regression, adjusting for potential confounding by age, birth cohort, calendar period and marital status. During 45.5 million person-years of follow-up 102,260 women were hospitalized with one or more autoimmune diseases. Overall, compared with childless women, women with children were at a relative risk of 1.04 (1.02-1.06) for any autoimmune diseases, 1.11 (1.08-1.14) for female predominant and 0.97 (0.95-1.00) for other autoimmune diseases. Possibly biologically related associations with parity were found for Hashimoto thyroiditis (1.11; 1.00-1.24), Graves' disease (1.19; 1.14-1.24), erythema nodosum (1.15; 1.01-1.32), psoriasis (1.08; 1.01-1.15), sarcoidosis (1.17; 1.06-1.28) and systemic lupus erythematosus (0.83; 0.74-0.93). Especially the one-year postpartum period was associated with an increased risk of Hashimoto thyroiditis, Graves' disease and sarcoidosis. Overall, parity was associated with an 11% increased risk of female predominant autoimmune diseases. Pregnancies resulting in liveborn children therefore seem to contribute only little to the general female predominance in autoimmune diseases. However, for a number of autoimmune diseases; especially autoimmune thyroid diseases, erythema nodosum and sarcoidosis parity might somehow be involved in disease development.
    Journal of Autoimmunity 08/2011; 38(2-3):J81-7. · 8.15 Impact Factor
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    ABSTRACT: Studies addressing possible socio-demographic and reproductive factors in the aetiology of osteoarthritis (OA) are few. We studied possible influences of educational level, household income, marital status and parenting patterns on OA risk overall and at anatomical sites. We linked national register data about socio-demographic variables, reproductive histories and OA hospital contacts to a cohort of 4.6 million Danes. Ratios of first OA hospitalisation rates (RRs) were calculated using Poisson regression. Overall, 100,437 women and 92,020 men had a first OA hospital contact during 91.5 million person-years between 1982 and 2008. Short education, low income and married status were significantly associated with increased OA risk, and persons with children were at higher risk of OA(overall) (RR=1.10 in women; RR=1.22 in men), OA(knee) (RRs 1.14; 1.28), OA(back) (RRs 1.18; 1.33), and OA(hand) (RRs 1.21; 1.43), but not of OA(hip) (RRs 0.96; 1.00) than persons without children. The RR of OA(overall) increased by a factor of 1.05 in women and 1.04 in men per additional child, most notably for OA(knee) in women (1.10 per child). Risk of OA hospitalisation was highest among married persons and persons with short education or low income. The similar or even stronger associations with reproductive factors in men than women suggest that unmeasured lifestyle factors rather than biological factors associated with pregnancy might explain the higher OA risk in persons with children. However, the particularly strong association between parity and risk of OA(knee) in women is compatible with a role of pregnancy-associated factors.
    Osteoarthritis and Cartilage 07/2011; 19(10):1176-82. · 4.26 Impact Factor
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    ABSTRACT: It has been suggested that reproductive factors may be involved in the etiology of multiple sclerosis (MS). We studied associations of reproductive history with MS risk in a population-based setting. Using national databases, we established a cohort comprising 4.4 million Danish men and women born between 1935 and 1989 and alive in 1968 or later. We obtained information about their live-born children, pregnancy losses, pregnancy complications, and infertility diagnoses. MS cases in the cohort were identified through 2004 in the Danish Register of Multiple Sclerosis. Associations between reproductive factors and MS risk were evaluated using rate ratios (RRs) obtained in log-linear Poisson regression analysis. MS was diagnosed in 6332 women and 3426 men. In both sexes, parents had a lower risk of MS compared with childless persons (in women, RR = 0.76 [95% confidence interval = 0.71-0.82]; in men, 0.89 [0.80-0.98]). RRs were inversely associated with number of children, age at first childbirth, and proximity in time since most recent birth. Among women, MS risk was unrelated to histories of pregnancy loss, pregnancy complications, or infertility. A supplementary analysis in which the date of MS diagnosis was backdated by 5 years to address the possibility of reverse causality did not confirm a protective effect of parenthood (in women, 0.95 [0.88-1.03]; in men, 1.08 [0.98-1.20]). Similar findings in women and men argue against a biologic role of pregnancy in the etiology of MS. Moreover, the observed differences in childbearing patterns were restricted to the 5 years before MS diagnosis, suggesting that reverse causality (ie, reduced reproductive activity in persons with yet-undiagnosed MS) might explain the observed associations.
    Epidemiology (Cambridge, Mass.) 07/2011; 22(4):546-52. · 5.51 Impact Factor
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    ABSTRACT: Studies have linked obesity, a sedentary lifestyle, and tobacco smoking to erectile dysfunction, but the evidence linking unhealthy lifestyle factors to other sexual dysfunctions or to sexual inactivity is conflicting. To examine associations between unhealthy lifestyle factors and sexual inactivity with a partner and four specific sexual dysfunctions in each sex. We used nationally representative survey data from 5,552 Danish men and women aged 16-97 years in 2005. Cross-sectional associations of lifestyle factors with sexual inactivity and sexual dysfunctions were estimated by logistic regression-derived, confounder-adjusted odds ratios (ORs). We calculated ORs for sexual inactivity with a partner and for sexual dysfunction and sexual difficulties overall in both sexes, for erectile dysfunction, anorgasmia, premature ejaculation, and dyspareunia in men, and for lubrication insufficiency, anorgasmia, dyspareunia, and vaginismus in women. Obesity (body mass index [BMI]≥30 kg/m(2) ) or a substantially increased waist circumference (men ≥102 cm; women ≥88 cm), physical inactivity, and, among women, tobacco smoking were each significantly associated with sexual inactivity in the last year. Among sexually active men, both underweight (BMI <20 kg/m(2) ) and obesity, a substantially increased waist circumference, physical inactivity in leisure time, high alcohol consumption (>21 alcoholic beverages/week), tobacco smoking, and use of hard drugs were each significantly positively associated with one or more sexual dysfunctions (ORs between 1.71 and 22.0). Among sexually active women, the only significant positive association between an unhealthy lifestyle factor and sexual dysfunction was between hashish use and anorgasmia (OR 2.85). In both sexes, several unhealthy lifestyle factors were associated with sexual inactivity with a partner in the last year. Additionally, among sexually active participants, men with unhealthy lifestyles were significantly more likely to experience sexual dysfunctions. Considering the importance of a good sex life, our findings may be useful in attempts to promote healthier lifestyles.
    Journal of Sexual Medicine 05/2011; 8(7):1903-16. · 3.51 Impact Factor
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    ABSTRACT: In a previous study, women with endometriosis were found to be at a 7-24-fold increased risk of multiple sclerosis (MS), systemic lupus erythematosus (SLE) and Sjögren syndrome (SS). We examined these associations in a large population-based cohort study. We followed 37 661 women registered with endometriosis in the Danish Hospital Discharge Register 1977-2007 for subsequent hospitalizations with MS, SLE or SS. As measures of relative risk, we used ratios of observed to expected incidence rates of first hospitalizations for MS, SLE and SS among women with endometriosis, i.e. standardized incidence ratios (SIR) with accompanying 95% confidence intervals (CIs). During slightly more than 456 000 person-years of follow-up, we identified 130, 54 and 86 cases of MS, SLE and SS, respectively, yielding SIRs of 1.2 (95% CI 1.05-1.5) for MS, 1.6 (1.2-2.1) for SLE and 1.6 (1.3-2.0) for SS. In a supplementary analysis restricted to 9191 women with laparoscopy or laparotomy confirmed endometriosis, associations were unchanged for MS (SIR = 1.4; 1.04-1.9), but lost statistical significance for SLE (SIR = 1.1; 0.6-2.1) and SS (SIR = 1.4; 0.9-2.3). Our national cohort-based findings do not support prior claims of markedly increased risks of MS, SLE and SS in women with endometriosis. However, whether women with endometriosis are truly at a modestly (20-60%) elevated risk of one or more of the studied autoimmune diseases must await clarification in future large-scale prospective studies.
    Human Reproduction 04/2011; 26(6):1555-9. · 4.67 Impact Factor
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    ABSTRACT: Studies have shown a high prevalence of sexual dysfunctions among individuals with a variety of health problems. To obtain a population-based assessment of these matters, we studied associations between indicators of physical and mental health problems and sexual dysfunctions in Denmark. We used questionnaire data from 4,415 sexually active men (mean age 48 years) and women (mean age 45 years) who participated in a nationally representative survey in 2005. Cross-sectional associations of overall health and physical and mental health problems with sexual dysfunctions in the last year were estimated by logistic regression-derived, confounder-adjusted odds ratios (OR(adj) ). We calculated OR(adj) with 95% confidence intervals (CI) for erectile dysfunction, anorgasmia, premature ejaculation, and dyspareunia in men, for lubrication insufficiency, anorgasmia, dyspareunia, and vaginismus in women, and for sexual dysfunction and sexual difficulties overall in both sexes. Sexual dysfunction was significantly more common among participants with poor self-rated health (OR(adj) 1.86, 95% CI 1.05-3.33 in men, OR(adj) 1.91, 1.08-3.37 in women). Physical health problems were significantly associated with male sexual dysfunctions (OR(adj) 1.75, 1.18-2.61), whereas mental health problems were significantly associated with female sexual dysfunctions (OR(adj) 2.59, 1.60-4.22). Among sexually active Danes, poor self-reported overall health is associated with increased rates of sexual dysfunction in both sexes, with physical health problems mainly affecting men's sex lives, and mental health problems being strongly associated with female sexual dysfunction.
    Journal of Sexual Medicine 12/2010; 8(7):1890-902. · 3.51 Impact Factor
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    ABSTRACT: Coinfection with multiple human papilloma virus (HPV) types is common in cervical HPV infection. To evaluate if infections with different HPV types occur independently, we examined 3558 women above 15 years of age suspected of cervical HPV infection. Among them, 1842 (52%) women were HPV negative and 1716 (48%) were HPV positive as analysed by a PCR-based commercial microarray assay for mucosal types. Of the HPV-positive samples, 824 (48%) had single infections, while 892 (52%) had multiple infections. Observed numbers of concurrent HPV types differed from expected numbers under the assumption of independence between infections by the various HPV types. Significant positive associations were observed for 16 pairs of HPV types in statistical analysis accounting for mass significance. Significant negative associations were also found, i.e. women with HPV-16 infection had 0.4 times the odds of having HPV-51 compared with women not infected with HPV-16. HPV-16 was the only type with odds ratios <1 for all pairwise combinations. While our findings of statistically significant coexistence do not prove biological dependence among HPV types, they do suggest that infections with some HPV types may depend on the existence of certain other HPV types. Any interaction between coexisting HPV types could either decrease or increase the efficacy of current HPV vaccines that offer mainly type-specific protection, depending on whether the types vaccinated against compete with other HPV types or not.
    Apmis 05/2010; 118(5):346-52. · 2.07 Impact Factor
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    ABSTRACT: Sexual dysfunctions and difficulties are common experiences that may impact importantly on the perceived quality of life, but prevalence estimates are highly sensitive to the definitions used. We used questionnaire data for 4415 sexually active Danes aged 16-95 years who participated in a national health and morbidity survey in 2005 to estimate the prevalence of sexual dysfunctions and difficulties and to identify associated sociodemographic factors. Overall, 11% (95% CI, 10-13%) of men and 11% (10-13%) of women reported at least one sexual dysfunction (i.e., a frequent sexual difficulty that was perceived as a problem) in the last year, while another 68% (66-70%) of men and 69% (67-71%) of women reported infrequent or less severe sexual difficulties. Estimated overall frequencies of sexual dysfunctions among men were: premature ejaculation (7%), erectile dysfunction (5%), anorgasmia (2%), and dyspareunia (0.1%); among women: lubrication insufficiency (7%), anorgasmia (6%), dyspareunia (3%), and vaginismus (0.4%). Highest frequencies of sexual dysfunction were seen in men above age 60 years and women below age 30 years or above age 50 years. In logistic regression analysis, indicators of economic hardship in the family were positively associated with sexual dysfunctions, notably among women. In conclusion, while a majority of sexually active adults in Denmark experience sexual difficulties with their partner once in a while, approximately one in nine suffer from frequent sexual difficulties that constitute a threat to their well-being. Sexual dysfunctions seem to be more common among persons who experience economic hardship in the family.
    Archives of Sexual Behavior 02/2010; 40(1):121-32. · 3.53 Impact Factor
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    ABSTRACT: The female predominance in systemic lupus erythematosus (SLE) suggests the possible involvement of reproductive factors in its etiology. We evaluated the relationship between parity and pregnancy losses and subsequent risk of SLE in a population-based cohort study. We followed 4.4 million Danes aged 15-69 years for first inpatient hospitalizations for SLE between 1977 and 2004. As measures of relative risk, we used Poisson regression-derived hospitalization rate ratios (RR) with 95% confidence intervals (CI) for cohort members with different reproductive histories. Overall, 1614 women and 274 men were hospitalized with SLE during 88.9 million person-years of followup. Number of children was unrelated to SLE risk in men, but women with at least one liveborn child were at lower risk than nulliparous women (RR 0.74; 95% CI 0.64-0.86), and women with 2 or more children were at lower risk than 1-child mothers. Recurrent idiopathic pregnancy losses, including spontaneous abortions, missed abortions, and stillbirths, were associated with markedly increased SLE risk (RR 3.50; 95% CI 2.38-4.96, for 2+ vs none; p < 0.001). Nulliparous women, 1-child mothers, and women who experience spontaneous abortions, missed abortions, or stillbirths are at increased SLE risk. Theoretically, immunological processes involved in subfertility or idiopathic pregnancy losses might act as initiating or contributing factors in some cases of SLE. However, considering the well established excess of pregnancy complications in women with established SLE, the observed associations more likely reflect the effect of subclinical immunological processes in women destined to develop SLE.
    The Journal of Rheumatology 07/2009; 36(9):1903-9. · 3.26 Impact Factor
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    ABSTRACT: While reproductive factors might plausibly be involved in the aetiology of rheumatoid arthritis (RA), the female predominance remains unexplained. A study was undertaken to address the possible impact of live births, pregnancy losses and pregnancy complications on the subsequent risk of RA in a nationwide cohort study. National register data were used to link reproductive histories and later RA hospitalisations in a cohort of 4.4 million Danes. As a measure of relative risk associated with different reproductive histories, ratios of first inpatient RA hospitalisation rates (RRs) were used with 95% confidence intervals (CIs) obtained by Poisson regression analysis. Overall, 7017 women and 3041 men were admitted to hospital with RA in 1977-2004 (88.8 million person-years). The risk of RA was inversely associated with age at birth of first child in both women and men (p for trend <0.001). Overall, nulliparity and a history of pregnancy loss were not associated with RA risk but, compared with one-child mothers, women with two (RR 0.84; 95% CI 0.78 to 0.90) or three (RR 0.83; 95% CI 0.77 to 0.91) children were at reduced risk. The risk of RA was increased in women with a history of hyperemesis (RR 1.70; 95% CI 1.06 to 2.54), gestational hypertension (RR 1.49; 95% CI 1.06 to 2.02) or pre-eclampsia (RR 1.42; 95% CI 1.08 to 1.84). One-child mothers and young parents are at increased risk of RA later in life, possibly due to socioeconomic factors. The novel finding of a significantly increased risk of RA in women whose pregnancies were complicated by hyperemesis, gestational hypertension or pre-eclampsia might reflect reduced immune adaptability to pregnancy in women disposed to RA or a role of fetal microchimerism in the aetiology of RA.
    Annals of the rheumatic diseases 04/2009; 69(2):358-63. · 8.11 Impact Factor
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    ABSTRACT: To determine whether the repeatedly observed low risk of ulcerative colitis after appendicectomy is related to the appendicectomy itself or the underlying morbidity, notably appendicitis or mesenteric lymphadenitis. Nationwide cohort studies. Sweden and Denmark. 709 353 Swedish (1964-2004) and Danish (1977-2004) patients who had undergone appendicectomy were followed up for subsequent ulcerative colitis. The impact of appendicectomy on risk was also studied in 224 483 people whose parents or siblings had inflammatory bowel disease. Standardised incidence ratios and rate ratios as measures of relative risk. During 11.1 million years of follow-up in the appendicectomy cohort, 1192 patients developed ulcerative colitis (10.8 per 100 000 person years). Appendicectomy without underlying inflammation was not associated with reduced risk (standardised incidence ratio 1.04, 95% confidence interval 0.95 to 1.15). Before the age of 20, however, appendicectomy for appendicitis (0.45, 0.39 to 0.53) or mesenteric lymphadenitis (0.65, 0.46 to 0.90) was associated with significant risk reduction. A similar pattern was seen in those with affected relatives, whose overall risk of ulcerative colitis was clearly higher than the background risk (1404 observed v 446 expected; standardised incidence ratio 3.15, 2.99 to 3.32). In this cohort, appendicectomy without underlying appendicitis did not modify risk (rate ratio 1.04, 0.66 to 1.55, v no appendicectomy), while risk after appendicectomy for appendicitis was halved (0.49, 0.31 to 0.74). In individuals with or without a familial predisposition to inflammatory bowel disease, appendicitis and mesenteric lymphadenitis during childhood or adolescence are linked to a significantly reduced risk of ulcerative colitis in adulthood. Appendicectomy itself does not protect against ulcerative colitis.
    BMJ (online) 02/2009; 338:b716. · 17.22 Impact Factor
  • BMJ (CR)-print. 01/2009; 338(7698):808.
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    ABSTRACT: The relationship between appendectomy and Crohn's disease is controversial. A Swedish-Danish cohort study was conducted to assess the risk of developing Crohn's disease after an appendectomy. 709 353 appendectomy patients in Sweden (since 1964) and Denmark (since 1977) were followed for first hospitalisations for Crohn's disease to 2004. Standardised incidence ratios (SIR) served as relative risks. Overall, 1655 Crohn's disease cases were observed during 11.1 million person-years of follow-up. Whereas appendectomy before the age of 10 years was not associated with the risk of Crohn's disease (SIR 1.00; 95% CI 0.80-1.25), the overall SIR of developing Crohn's disease was 1.52 (95% CI 1.45-1.59), being highest in the first 6 months (SIR 8.69; 95% CI 7.68-9.84). SIR diminished rapidly thereafter, with the risk of Crohn's disease reaching background levels after 5-10 years for Crohn's disease overall, as well as for Crohn's ileitis, ileocolonic Crohn's disease, Crohn's colitis and other/unspecified Crohn's disease. A long-term increased risk of Crohn's disease up to 20 years after the appendectomy was seen only in appendectomy patients without appendicitis or mesenteric lymphadenitis. The transient increased risk of Crohn's disease after an appendectomy is probably explained by diagnostic bias.
    Gut 11/2007; 56(10):1387-92. · 10.73 Impact Factor