Antihypertensive therapy and incidence of type 2 diabetes: a systematic review.

OBJECTIVE To systematically review the available evidence examining the effects of the major antihypertensive drug classes on the incidence of type 2 diabetes. RESEARCH DESIGN AND METHODS The Cochrane Controlled Trials Register, Medline, and Embase were searched for English-language case-control, cohort, and randomized controlled trials involving the major antihypertensive classes and reporting type 2 diabetes as an end point. Reference lists of original studies and narrative reviews were also hand searched. One reviewer (R.P.) performed the electronic searches. Both reviewers independently extracted data and assessed all potentially relevant studies for inclusion and methodological quality. Abstracts were not included, and unpublished studies were not sought. RESULTS One case-control study, 8 cohort studies, and 14 randomized controlled trials met inclusion criteria. No study examined diabetes incidence as a primary end point. Poor methodological quality limits the conclusions that can be drawn from most nonrandomized trials. Evidence from randomized studies is also potentially limited by several sources of bias, including treatment contamination and bias inherent in post hoc analyses. Data from the highest-quality studies suggest that diabetes incidence is unchanged or increased by thiazide diuretics and beta-blockers and unchanged or decreased by ACE inhibitors, calcium channel blockers, and angiotensin receptor blockers. CONCLUSIONS The major antihypertensive classes may exert differential effects on diabetes incidence, although current data are far from conclusive. Ongoing placebo-controlled randomized trials involving potentially beneficial drug classes and examining diabetes incidence as a primary end point should provide more definitive evidence.