The Nurses’ Health Study, established in 1976 by Dr. Frank Speizer, and the Nurses’ Health Study II, established in 1989 by Dr. Walter Willett, are the most definitive long-term epidemiological studies conducted to date on older women’s health.

The study has followed 121,700 female registered nurses since the mid-1970s to assess risk factors for cancer and cardiovascular disease. The studies are among the largest investigations into risk factors for major chronic diseases in women ever conducted.

The studies include clinicians, epidemiologists, and statisticians at the Channing Laboratory. Participating organizations from the Massachusetts medical community include the Harvard Medical School, Harvard School of Public Health, Brigham and Women’s Hospital, Dana Farber Cancer Institute, Boston Children’s Hospital, and Beth Israel Deaconess Medical Center.

In 1980, assessments of diet, aspirin use, and colon examination were added to the original study.