The Nurses' Health Study

A second well-known cohort study is the Nurses' Health Study, which was developed by Harvard University and Brigham and Women's Hospital. The study began in 1976 with a cohort of 121,700 female nurses, 30 to 55 years of age, living in the United States.²⁰ Initially designed to ex­plore the relationship between oral contraceptives and breast cancer, nurses in the study have provided answers to detailed questions about their menstrual cycle, smoking habits, diet, weight and waist measurements, activity pat­terns, health problems, and medication use. They have collected urine and blood samples and even provided re­searchers with their toenail clippings.²¹ In selecting the co­hort, it was reasoned that nurses would be well organized, accurate, and observant in their responses and that phys­iologically they would be no different from other groups of women. It also was anticipated that their childbearing,

Framingham Study: Significant Milestones

• 1960—Cigarette smoking found to increase risk of
heart disease

• 1961—Cholesterol level, blood pressure, and
electrocardiogram abnormalities found to increase
risk of heart disease

• 1967—Physical activity found to reduce risk of heart
disease and obesity to increase risk of heart disease

• 1970—High blood pressure found to increase risk of
stroke

• 1976—Menopause found to increase risk of heart
disease

• 1977—Effects of triglycerides and low-density
lipoprotein (LDL) and high-density lipoprotein
(HDL) cholesterol noted

• 1978—Psychosocial factors found to affect heart
disease

• 1986—First report on dementia

• 1988—High levels of HDL cholesterol found to
reduce risk of death

• 1994—Enlarged left ventricle shown to increase risk
of stroke

• 1996—Progression from hypertension to heart failure
described

• 1997—Report of cumulative effects of smoking and
high cholesterol on the risk of atherosclerosis

(Abstracted from Framingham Heart Study. [2001]. Research milestones. [On-line.] Available: http://rover.nhlbi.nih.gov/ about/framingham/timeline.htm.)

eating, and smoking patterns would be similar to those of other working women.

The Nurses' Health Study has yielded over 250 pub­lished papers on subjects as diverse as body mass index, weight change, and risk for adult-onset asthma in women²²; smoking cessation and time course to decreased risk for coronary heart disease in middle-aged women²³; electric blanket use and breast cancer²⁴; waist circumference, waist: hip ratio, and risk for breast cancer²⁵; and aspirin and risk for colorectal cancer.²⁶ After 25 years, 90% of the nurses still respond promptly to the biennial question­naire—a rate that far exceeds the average for other longi­tudinal studies.