The Nurses' Health Study began in 1976, when 121,700 female registered nurses living in eleven states completed a mailed questionnaire that included items about their medical history and risk factors for cancer. The National Cancer Institute funded the first three years of the study and subsequent years on data pertaining to cancer. In 1980 the National Heart, Lung, and Blood Institute began funding the cardiovascular portion of the study. Follow-up questionnaires have been administered every two years subsequently.