The Chronic Disease Epidemiology Unit has developed several very large study populations which have been followed longitudinally, with a total sample size of approximately 280,000 subjects.
All three cohorts are followed through biennial questionnaires which gather repeated detailed information about diet, activity, other lifestyle variables, and health, including medications. These assessments have been carefully validated and calibrated. We also collect information on quality of life mental health social factors. Many disease outcomes (cancers, stroke, coronary disease, etc.) are documented through medical records. Other important outcomes are confirmed through supplementary questionnaires (e.g. diabetes, fractures, etc.) or through testing (cognitive function). About a third of each cohort provided blood samples (for plasma, DNA, red cells), with a repeated collection in the Nurses. In addition, we collected salivary DNA on thousands of participants who did not provide blood, and we collect tumor tissue for many of the cancers. All three cohorts continue to be followed with follow-up rates of about 90% for completion of questionnaires, and about 98% complete follow-up for mortality.