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Blood Pressure Lowering in Type 2 Diabetes: A Systematic Review and Meta-Analysis | Journal Scan
Study Questions:
What is the association between blood pressure (BP)–lowering treatment and vascular disease in type 2 diabetes?
Methods:
A MEDLINE search was performed for large-scale randomized controlled trials of BP–lowering treatment including patients with diabetes (type 1 diabetes trials were excluded), published between January 1966 and October 2014. Estimates were stratified by baseline BP and achieved BP, and pooled using fixed-effects meta-analysis. Primary outcomes included all-cause mortality, cardiovascular events, coronary heart disease events, stroke, heart failure, retinopathy, new or worsening albuminuria, and renal failure.
Results:
Forty trials with 100,354 participants were included. Twelve studies had at least 3,000 subjects. Each 10 mm Hg lower systolic BP (sBP) was associated with a significantly lower risk of mortality (relative risk [RR], 0.87), cardiovascular events (RR, 0.89), coronary heart disease (RR, 0.88), and stroke (RR, 0.73). The associations for heart failure events and renal failure were not significant. For microvascular outcomes, a 10 mm Hg lower sBP was associated with a lower risk of retinopathy (RR, 0.87) and albuminuria (RR, 0.83). The corresponding number needed to treat over 10 years for all-cause mortality was 32, cardiovascular disease events 26, coronary heart disease events 55, stroke 25, retinopathy 45, and for albuminuria 11. When trials were stratified by baseline mean sBP at greater than or less than 140 mm Hg, RRs for outcomes other than stroke, retinopathy, and renal failure were lower in studies with greater baseline sBP (p interaction <0.1). The associations between BP-lowering treatments and outcomes were not significantly different, irrespective of drug class, except for stroke which was less on calcium channel blockers and increased on beta-blockers, heart failure which was reduced in those on diuretics and angiotensin-receptor blockers (ARBs), and a lower risk of mortality with ARBs vs. beta-blockers which was driven by the LIFE study.
Conclusions:
Among patients with type 2 diabetes, BP lowering was associated with improved mortality and other clinical outcomes, with lower RRs observed among those with baseline BP of 140 mm Hg and greater. These findings support the use of medications for BP lowering in these patients.
Perspective:
The recent guidelines relaxed the threshold for initiation of BP treatment from 130 to 140 mm Hg, which was triggered by the ACCORD trial that found no reductions in major cardiovascular events with a target sBP <120 compared to <140 mm Hg. In this review, although proportional associations of BP–lowering treatment for most outcomes studied were attenuated below a sBP level of 140 mm Hg, data indicate that further reduction below 130 mm Hg is associated with a lower risk of stroke, retinopathy, and albuminuria, potentially leading to net benefits for many individuals at high risk for those outcomes.
Keywords: Albuminuria, Angiotensin Receptor Antagonists, Blood Pressure, Calcium Channel Blockers, Coronary Disease, Diabetes Mellitus, Type 2, Diuretics, Heart Failure, Hypotension, Renal Insufficiency, Stroke, Risk
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