Data collection. Trained personnel visited all cases and controls
at their homes for the collection of dietary and health information,
anthropometric measurements, and biological specimens. Sociodemographic
characteristics, smoking, socioeconomic status, physical
activity, and medical history data were collected during an interview
using a questionnaire with close-ended questions. Self-reported diabetes
and hypertension were validated using the recommended definitions
by the Expert Committee on the Diagnosis and Classification
of Diabetes Mellitus (25), and the Third Joint National Committee
on Detection, Evaluation, and Treatment of High Blood Pressure
(26). We computed sensitivities, specificities, and positive and negative
predictive values from the questionnaire data and measurements
of blood pressure and blood sugar. These variables showed that
self-reported assessments of diabetes and hypertension were reliable
in this population (21).