Review finds blood pressure-lowering effects weaker in patients with type 2 diabetes

Absolute risk reductions did not differ substantially between people with and without type 2 diabetes because of the higher absolute cardiovascular risk among those with the condition, according to a new meta-analysis.

Relative beneficial effects of reducing blood pressure were weaker in patients with type 2 diabetes than in those without, but absolute effects were similar, a meta-analysis found.

Researchers investigated the effects of lowering blood pressure on major cardiovascular events by type 2 diabetes status, as well as by baseline levels of systolic blood pressure, via a one-stage individual participant-level data meta-analysis of major randomized controlled trials. Trials compared blood pressure-lowering medications versus placebo or other classes of blood pressure-lowering medications, or an intensive versus a standard blood pressure-lowering strategy. Results were published July 22 by The Lancet Diabetes and Endocrinology.

The researchers measured the effect per 5-mm Hg reduction in systolic blood pressure on the risk for a major cardiovascular event (first fatal or nonfatal stroke or cerebrovascular disease, fatal or nonfatal ischemic heart disease, or heart failure causing death or requiring hospitalization). Hazard ratios (HRs) were stratified by type 2 diabetes status at baseline, with further stratification by baseline categories of systolic blood pressure in 10-mm Hg increments from 120 mm Hg to 170 mm Hg. The effect of each of the five major blood pressure-lowering drug classes, including angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, beta-blockers, calcium-channel blockers, and thiazide diuretics, was estimated.

The meta-analysis included data from 51 randomized clinical trials published between 1981 and 2014 involving 358,533 participants (58% men), of whom 103,325 (29%) had type 2 diabetes at baseline. The baseline mean blood pressure was 149/84 mm Hg in those with type 2 diabetes and 153/88 mm Hg in those without. Over a median follow-up of 4.2 years, a 5-mm Hg reduction in systolic blood pressure decreased the risk of major cardiovascular events in both groups, but the relative treatment effect was weaker in participants with type 2 diabetes (HR, 0.94; 95% CI, 0.91 to 0.98) than in those without (HR, 0.89; 95% CI, 0.87 to 0.92).

However, absolute risk reductions did not differ substantially between patients by diabetes status because of the higher absolute cardiovascular risk among patients with diabetes. Relative treatment effects did not differ substantially by diabetic status for any of the drug classes investigated. Because the relative risk reduction was not related to blood pressure or different drug classes, using different blood pressure thresholds, intensities of blood pressure lowering, or drug classes in patients with diabetes is not warranted, the study authors wrote.

An editorial cautioned that such conclusions are complicated by the difficulty of getting accurate blood pressure measurements and by new oral diabetes drugs (sodium-glucose cotransporter-2 inhibitors and finerenone) that have shown direct positive effects on chronic kidney disease and cardiovascular disease, leading the editorialists to advise that “determining accurate blood pressure measurement and appropriate drug selection for people with type 2 diabetes will require careful consideration.”