Sexual habits before multiple sclerosis: a national case-control study.

UNLABELLED The trigging off agent for multiple sclerosis (MS) is despite intensive epidemiological and biomedical research still unknown. The disease is typically diagnosed in reproductive age and recent findings have suggested that MS could be a sexually transmitted disease. AIM To assess the influence of different sexual practices in young age on the risk of developing MS, and specifically to explore the possible impact of oral sex and oral sperm exposure on this risk. DESIGN National case-control study. METHODS Inclusion: Danish women with a first time MS discharge diagnosis from a neurological department at most 40 years old during the period 1998-2005, and an age and geographically matched control group. The response rate to our postal questionnaires was 75% for cases and 61% for controls. A total of 604/619 completed case/control questionnaires were included in the analysis. Data underwent logistic regression analysis. RESULTS We found no difference between women with and without MS for years of schooling, oral herpes infections, genital herpes, blood transfusions, age at sexual debut, age at coital debut, number of sexual partners before and after age 20 years, anal sex, condyloma attack or chlamydia infections. Family disposition with an affected father, mother or sibling, increased the risk of MS 9.1, 6.9 and 4.1 times, respectively. A total of 68% of cases and of 72% of controls had oral sex sometimes or often before their 20th year. Among women entertaining oral sex, 53%, respectively, 54% had experienced oral sperm exposure. Also oral sex after 20 years was similar in women with and without MS. CONCLUSION Neither oral sex in early reproductive age, oral sperm exposure, oral sex after 20 years, sexual debut, nor number of sexual partners had any association to the risk of later developing MS. This study does not support the hypothesis that MS is a sexually transmitted or acquired disease.