Demographic data were collected at baseline.
Clinical and laboratory data were obtained at
baseline and every 3 months thereafter. A structured interview was used in both groups every
3 months to obtain self-reported cardiovascular
disease outcomes. Although the interviewers
were aware of the study-group assignments, they
used the same format for interviews in the two
groups to minimize ascertainment bias. Medical
records and electrocardiograms were obtained
for documentation of events. Whenever clinicalsite staff became aware of a death, a standard
protocol was used to obtain information on the
event.