medwireNews: The absolute benefit of blood pressure reduction on cardiovascular risk does not differ according to whether or not people have type 2 diabetes, shows an individual participant data meta-analysis.
Kazem Rahimi (University of Oxford, UK) and colleagues from the Blood Pressure Lowering Treatment Trialists’ Collaboration analyzed 358,533 participants of 51 randomized clinical trials and found that the 29% who had type 2 diabetes achieved a smaller relative benefit from antihypertensive treatment than those who did not.
The primary combined endpoint was first fatal or nonfatal ischemic heart disease or cerebrovascular disease/stroke, or hospitalization or death due to heart failure. Among people without diabetes, this occurred at a rate of 7.8 per 100,000 person–years in those in the intervention group versus 9.3 per 100,000 person–years in the control group. This equated to a significant 11% reduction in cardiovascular risk per 5 mmHg reduction in blood pressure.
By contrast, among people with diabetes the corresponding event rates were higher, at 13.9 and 15.5 per 100,000 person–years, but the cardiovascular risk reduction per 5 mmHg reduction in blood pressure was markedly smaller, at 6%.
“However, this result was not because lowering blood pressure to below a certain threshold was ineffective or harmful,” write the researchers in The Lancet Diabetes & Endocrinology.
“Indeed, across the full spectrum of baseline blood pressure categories, there was no subgroup in which harmful effects on major cardiovascular outcomes were detected.”
At baseline, people with diabetes had blood pressure lower than those without, at 149/84 mmHg versus 153/88 mmHg, but they were more likely to be already taking antihypertensives.
Looking at individual endpoints, the team found that blood pressure reduction did not significantly reduce ischemic heart disease risk in people with diabetes, which accounted for the weaker effect on the combined endpoint compared with that seen in those without diabetes.
This difference disappeared when considering absolute risk; because of the higher event rates in people with versus without diabetes, blood pressure reduction prevented a similar number of events in both groups.
However, the researchers found a persistent difference for cardiovascular death – both relative and absolute. The risk for this outcome did not decrease with blood pressure reduction in people with diabetes, but did in those without.
Given their overall findings, Rahimi and team believe it is not necessary to apply specific blood pressure thresholds, treatment intensities, or medication classes in people with type 2 diabetes.
Writing in a linked commentary, Luis Ruilope and Gema Ruiz Hurtado, both from Hospital Universitario 12 de Octubre in Madrid, Spain, broadly agree with this statement.
But they stress: “Discussions about blood pressure control will not be complete until we move beyond standard in-office blood pressure measurement.
“In-office blood pressure measurement is the only validated technique and frequently does not recognise the phenotypes of hypertension observed in out-of-office blood pressure measurements (eg, so-called white coat and masked hypertension), and therefore can give a false value of the real blood pressure of the patient.”
The commentators also note that the meta-analysis does not account for the recently revealed effects of sodium-glucose cotransporter 2 inhibitors and finerenone on blood pressure and cardiorenal outcomes.
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