Nurses’ Health Study
The Nurses’ Health Study is a long-term cohort study that has collected information about cardiovascular and other disease risk factors, in addition to lifestyle factors, since its beginning in 1976 (Belanger et al. 1978). At the onset, 121,701 female registered nurses, aged 30–55 years, completed a questionnaire about their medical history and disease risk factors. The cohort has been followed up every 2 years with mailed questionnaires that update exposure information and inquire about newly diagnosed medical illnesses. Numerous analyses involving NHS data have been performed, including investigation of the impact of smoking cessation on long-term risks of coronary artery disease (Kawachi et al. 1994) and relationship between phobic anxiety and coronary heart disease events (Albert et al. 2005).