The LEADER trial in type 2 diabetes: Were the characteristics and outcomes of the participants representative?

AIMS: To compare the characteristics and outcomes of people with type 2 diabetes recruited to the LEADER trial to those of participants in the contemporaneous community-based Fremantle Diabetes Study Phase II (FDS2) who fulfilled LEADER entry criteria. METHODS: Baseline characteristics of LEADER and LEADER-eligible FDS2 participants were compared using bivariate methods. Incidence rates of the primary (nonfatal myocardial infarction, nonfatal stroke, cardiovascular disease (CVD) death) and other outcomes in the LEADER placebo group were compared with those in LEADER-eligible FDS2 participants during 3.8 years after entry, the median LEADER follow-up. RESULTS: Of 1551 FDS2 type 2 participants, 323 (20.8%) were LEADER-eligible. Compared with the LEADER sample, they were an average 6 years older, and were less likely to be male, obese and to have prior CVD. There were 3.9 and 2.9 primary outcomes/100 patient-years in LEADER placebo-treated and FDS2 LEADER-eligible patients, respectively. Incidence rates for first myocardial infarction and stroke were 1.9 and 2.1 events/100 patient-years and 1.1 and 1.0 events/100 patient-years, respectively. FDS2 LEADER-eligible patients had a lower CVD death rate of 0.8 versus 1.6/100 patient-years in the LEADER placebo group, but their non-CVD mortality was greater (2.1 versus 1.0/100 patient-years). CONCLUSIONS: These data suggest recruitment bias in type 2 diabetes CVD outcome trials.