Participants were examined by trained research nurses, either at home or in the hospital. The nurses measured height, body weight, waist circumference and blood pressure. Self-administered questionnaires were used to collect data on the disease history and about current health, medication, dietary pattern, physical activity, smoking pattern and alcohol consumption. Annual interviews by phone about changes in health status and medication use and registries containing information on vital status and causes of death kept the patient information up to date.
In addition, blood samples were collected for the measurement of blood glucose, total cholesterol, HDL cholesterol, triglycerides and the fatty acid composition of cholesteryl esters. The blood samples were mailed to the lab, where they were analyzed and stored within 48 hours.