Large Cohorts: Toward Routine Databases for Public Health Science.

In 1985, Per Magnus was hired by the Norwegian medical and social science research councils to figure out how epidemiological research could best be developed in Norway. Magnus was a young physician with a PhD, a specialty in medical genetics, and an extraordinary talent and interest in science. To complete his mission, he chose to travel to six countries to interview epidemiologists. At Harvard University, he spoke with Walter Willett.1 In his report from 1986, Magnus wrote that Willett was responsible for implementation of a large prospective study on the effect of nutrition on disease later in life. This study, according to Magnus, would recruit 60 000 male health professionals. They would receive a comprehensive questionnaire on nutrition and be followed up every other year onwards. The study was modeled on the Nursesu0027 Health Study (NHS), a similar study of 120 000 nurses who had been followed successfully biannually since 1976. According to the report, Willett was convinced that if one wanted progress in epidemiological research on chronic diseases, it was vital to develop large, prospective cohort studies. Such cohorts would provide much stronger evidence than smaller inconclusive studies. Therefore one should not scatter and waste funding on small studies, said Willett.