Incidence of Type 2 Diabetes With Verapamil Compared With Other Calcium Channel Blockers

OBJECTIVE Evidence that the calcium channel blocker (CCB) verapamil slows type 1 diabetes progression suggests possible preventive benefits among people at risk of developing type 2 diabetes. We compared type 2 diabetes incidence between users of verapamil versus other CCBs in a population-based cohort. RESEARCH DESIGN AND METHODS From a random sample of Australians in national subsidized health care databases, we identified 90,026 individuals who initiated treatment with a CCB (at least two supplies) between July 2003 and December 2014. Incident diabetes was captured by subsequent receipt of glucose-lowering treatment or registration with the National Diabetes Services Scheme. Individuals were followed from first CCB supply until discontinuation, diabetes onset, death, or end of 2014. Multistate Poisson regression models characterized associations of CCB subclass with type 2 diabetes incidence and death (the competing event), after multivariable propensity score adjustment. RESULTS The cohort comprised 4,485 verapamil users (5.0%) and 85,541 treated with other CCBs (mostly dihydropyridines). During a median 1.6-year follow-up, 101 individuals treated with verapamil developed type 2 diabetes (8.8 per 1,000 person-years) compared with 2,622 people treated with other CCBs (11.4 per 1,000 person-years). This translated to an incidence rate ratio of 0.77 (95% CI 0.63–0.94) in favor of verapamil (fully adjusted) and a lower probability of type 2 diabetes at 6 years (4.2% [95% CI 3.3–5.3] vs. 5.4% [4.7–6.3] for a typical clinical profile; absolute risk difference 1.3% [95% CI –0.1–2.4]). Results were robust across multiple sensitivity analyses. CONCLUSIONS Verapamil use is associated with a lower incidence of type 2 diabetes compared with other CCBs.