Harvard Cohort Studies
The large, long-running Harvard cohort studies have played an important role over the years in helping to define what makes up a “healthy lifestyle.”  By following a large group of people (or cohort) over time, these studies provide detailed insight into the factors that lower (and raise) the risk of cancer, heart disease, stroke, diabetes, and other diseases. 

The Harvard Center for Cancer Prevention works closely with several Harvard cohort studies:

Nurses' Health Study
The Nurses' Health Study has followed the health of a group of more than 120,000 female nurses for over the last 30 years. It is among the largest studies of its kind to look at the risk factors for chronic disease in women.

Nurses' Health Study II
Daughter of the original, the Nurses’ Health Study II was started 1989 to look at risk factors in a younger generation of women--in particular, to study the relationship between the pill (oral contraceptives) and chronic disease. The Nurses’ Health Study II includes 115,000 female nurses.

Health Professionals Follow-Up Study
The all-male complement to the Nurses' Health Study, the Health Professionals Follow-Up Study started in 1986 to investigate the risk factors for major chronic disease in men.  The study includes over 50,000 male health professionals.