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Everyone in public health has heard of the first Nurses' Health Study (NHS). This cohort of 121 700 nurses assembled in 1976 has generated a substantial part of what we know today about women's health and the prevention of chronic diseases. A brilliant and competent team of investigators from Harvard University originated it 40 years ago and have conducted it since then, but as every epidemiologist knows, wonderful ideas do not necessarily translate into great studies. The NHS is the encounter of a wonderful idea (i.e., enrolling nurses in a large cohort study) and the historically outstanding response from nurses, who made the study theirs. Nurses joined, persisted, and used their unique and essential skills to make this cohort study an exemplar.
BEYOND DOCTORS
The inspiration for the NHS came from the British Doctor's Study (BDS), which originally involved just a half-page questionnaire about smoking that was filled out in 1951 by around 30 000 male doctors, whose subsequent deaths were tracked with the help of the British Medical Association. In 1966, Frank Speizer went as Research Associate to the Statistical Research Unit, in London, with Richard Doll, who was the leading investigator of the BDS. Back at Harvard in 1968, Speizer wanted to study the health effects of oral contraceptives (OCs). This was a timely question because in 1960 virtually no women used oral contraception. By 1976, most young women had used oral contraceptives at some point in their lives. Unraveling OCs' long-term health effects warranted investment in a large cohort study. A first attempt, which took place in 1971, consisted in enrolling the wives of US doctors. But too many (maybe 15%-20%) of the questionnaires sent to the wives were filled out by their husbands. This design did not work. That is when the idea of nurse participants came about.
The design itself was extremely audacious. The 1970s and 1980s were the heydays of case-control studies. Once properly understood-thanks to the great insights of people such as Jerome Cornfield and Olli Miettinen-the design was enormously attractive. With only a few thousand...