Each 10-mm Hg decrease in systolic blood pressure (BP) among patients with type 2 diabetes significantly lowered rates of mortality and several adverse events, including cardiovascular (CV) events and stroke, new data from a large study published in JAMA suggest.
The aim of the study was to examine whether there is an association between BP–lowering treatment and vascular disease in patients with type 2 diabetes, since lowering BP is a widely used strategy to reduce vascular risk in this patient population.
Investigators searched Medline for studies of large randomized trials that tested BP-lowering treatment in patients with diabetes published from January 1966 to October 2014. The main outcome measures were all-cause mortality, CV events, coronary heart disease (CHD) events, stroke, heart failure, retinopathy, new or worsening albuminuria, and renal failure.
The analysis included 40 trials and 100,354 patients.
For each 10-mm Hg drop in systolic BP, there were significantly lower rates of the following events:
- Mortality (relative risk [RR]=0.87; 95% CI, 0.78-0.96; absolute risk reduction [ARR] in events per 1,000 patient-years=3.16; 95% CI, 0.90-5.22)
- CV events (RR=0.89; 95% CI, 0.83-0.95; ARR=3.90; 95% CI, 1.57-6.06)
- CHD events (RR=0.88; 95% CI, 0.80-0.98; ARR=1.81; 95% CI, 0.35-3.11)
- Stroke (RR=0.73; 95% CI, 0.64-0.83; ARR=4.06; 95% CI, 2.53-5.40)
- Albuminuria (RR=0.83; 95% CI, 0.79-0.87; ARR=9.33; 95% CI, 7.13-11.37)
- Retinopathy (RR=0.87; 95% CI, 0.76-0.99; ARR=2.23; 95% CI, 0.15-4.04)
Researchers stratified trials by mean baseline systolic BP at greater than or less than 140 mm Hg and found that RRs for outcomes, except stroke, retinopathy and renal failure, were reduced in studies with greater baseline systolic BP (P for interaction<.1).
In addition, associations between BP-lowering treatments and outcomes, not including stroke and heart failure, were similar, regardless of drug class.
“These findings support the use of medications for BP lowering in these patients [with type 2 diabetes],” the researchers concluded. “Although proportional associations of BP-lowering treatment for most outcomes studied were attenuated below a systolic BP 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.”
Commenting on the study, Bryan Williams, MD, of the University College London, wrote in an accompanying editorial that the study is timely, clear and important, and supports current guideline recommendations.
“However, the findings of the study … suggest that for some patients, [guideline] treatment thresholds and targets might be too conservative, especially for optimally reducing the risk of stroke and the development or progression of albuminuria,” he wrote.
“This conundrum highlights the problems with clinician overreliance on guidelines and guideline overdependence on an often uncritical adoption of evidence, despite the limitations of the clinical trials.”
Dr. Williams noted that going forward, a better understanding of genetic markers and phenotypic manifestations that predict the evolution of BP-mediated disease in patients with diabetes is needed to facilitate the design of trials that can determine the effects of earlier and more aggressive BP lowering.
“The information to address these important issues will not emerge from ever more aggressive treatment in older and frail patients with disease beyond the point of no return,” he wrote. “To try and do so would not advance the care and improve outcomes for younger patients with diabetes.”