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Original Contribution
September 2005

Recent Use of Oral Contraceptives and the Risk of Multiple Sclerosis

Author Affiliations

Author Affiliations: Departments of Epidemiology (Drs Alonso, Ascherio, and Hernán) and Nutrition (Dr Ascherio), Harvard School of Public Health, and Channing Laboratory, Brigham and Women’s Hospital (Dr Ascherio), Boston, and Boston Collaborative Drug Surveillance Program, Boston University (Drs S. S. Jick and H. Jick) Lexington, Mass; and Department of Neurology, College of Medicine, University of California, Irvine (Dr Olek).

Arch Neurol. 2005;62(9):1362-1365. doi:10.1001/archneur.62.9.1362

Background  Exogenous estrogens affect the onset and clinical course of experimental allergic encephalomyelitis. Oral contraceptives, a frequent source of exogenous estrogens in humans, could have a role in the development of multiple sclerosis (MS).

Objective  To examine whether recent oral contraceptive use and pregnancy history are associated with the risk of MS.

Design and Setting  A case-control study nested in the General Practice Research Database. This database contains prospective health information (drug prescriptions and clinical diagnoses) on more than 3 million Britons who are enrolled with selected general practitioners.

Participants  One hundred six female incident cases of MS, younger than 50 years, with at least 3 years of continuous recording in the General Practice Research Database before the date of first symptoms (index date), identified between January 1, 1993, and December 31, 2000, and 1001 controls matched on age, practice, and date of joining the practice.

Main Outcome Measure  Incidence of first symptoms of MS, confirmed through medical records.

Results  The incidence of MS was 40% lower (odds ratio, 0.6; 95% confidence interval, 0.4-1.0) in oral contraceptive users compared with nonusers during the previous 3 years. The risk of MS increased in the 6 months after pregnancy (odds ratio, 2.9, 95% confidence interval, 1.2-6.6), but it was not otherwise related to parity.

Conclusions  The hormonal changes that occur during oral contraceptive use and pregnancy may be associated with a short-term reduction in the risk of MS, and the postpartum period may be associated with a short-term increase in the risk of MS.