The Nurses' Health Study original cohort was established in 1976 by Dr. Frank Speizer. Initially, the study investigated contraceptive use, smoking, cancer, and cardiovascular disease. The 1976 baseline group included married female registered nurses between the ages of 30 and 55. Approximately 121,700 participants in 11 of the most populous U.S. states (California, Connecticut, Florida, Maryland, Massachusetts, Michigan, New Jersey, New York, Ohio, Pennsylvania, and Texas) responded. The survey was then distributed biennially thereafter. Over the years, the principal investigator of the Nurses' Health Study have been Frank Speizer, Graham Colditz, Sue Hankinson, and Meir Stampfer.