The Nurses’ Health Study (NHS) cohort was established in 1976, when 121,700 female registered nurses aged 30 to 55 years completed a baseline questionnaire including items on risk factors for cancer and cardiovascular disease. Every 2 years, follow-up questionnaires have been sent to update risk factor information and disease development. Based upon self-report, the NHS population is predominantly White (93.7% White, 2% Black, 0.7% Asian, and 3.6% other/unknown) reflecting the demographics of registered nurses in the United States in 1976. Follow-up has been extremely high with 4.4% of person-time lost to follow-up. We routinely search the National Death Index every two years for non-responders.14 In 1976, written informed consent was not required; instead, return of completed questionnaires was considered consent to enroll on the study. The Institutional Review Board of the Brigham and Women's Hospital reviewed and approved the study protocol.
