BP reduction lowers cardiovascular risk regardless of diabetes status: Lancet

UK: A blood pressure reduction of 5mm Hg lowers the risk of major cardiovascular (CV) events that are comparable in patients with or without type 2 diabetes, a meta-analysis has revealed. 

The researchers wrote in the study published in The Lancet Diabetes and Endocrinology, "Although the relative beneficial effects of blood pressure reduction on major cardiovascular events were slightly smaller in patients with type 2 diabetes compared to those without, absolute effects were similar." The study was a meta-analysis from the Blood Pressure Lowering Treatment Trialists' Collaboration (BPLTTC). 

There is an ongoing debate on whether the threshold for blood pressure-lowering treatment should be different between people with and without type 2 diabetes. Milad Nazarzadeh, Deep Medicine, Oxford Martin School, University of Oxford, Oxford, UK, and colleagues, therefore, aimed to investigate the effects of blood pressure-lowering treatment on the risk of major cardiovascular events by type 2 diabetes status, as well as by baseline levels of systolic blood pressure.

For this purpose, the researchers conducted a one-stage individual participant-level data meta-analysis of major randomized controlled trials using the dataset of Blood Pressure Lowering Treatment Trialists' Collaboration. Trials with information on type 2 diabetes status at baseline were included if they 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, and reported at least 1000 persons-years of follow-up in each group. 

The primary outcome was the treatment effect per 5 mm Hg reduction in systolic blood pressure on the risk of developing a major cardiovascular event. This was defined as the first occurrence of fatal or non-fatal stroke or cerebrovascular disease, fatal or non-fatal ischaemic heart disease, or heart failure causing death or requiring hospitalization. 

A network meta-analysis framework was used to estimate the effect of each of the five major blood pressure-lowering drug classes, including angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, β blockers, calcium channel blockers, and thiazide diuretics. 

The researchers included data from 51 randomized clinical trials published between 1981 and 2014 consisting of 358 533 participants (58% men), among whom 103 325 (29%) had known type 2 diabetes at baseline. 

"Despite the weaker relative effect in type 2 diabetes, the absolute risk reductions were broadly similar in those with type 2 diabetes and those without, this difference in relative risk was not related to baseline blood pressure or allocation to different drug classes," the authors wrote in their study. 

"These findings emphasise the importance of BP lowering for cardioprotection before the onset of type 2 diabetes. The current blood pressure thresholds for initiation of blood pressure treatment do not seem to be justified in people with established type 2 diabetes." 

"This study calls for the removal of specific blood pressure thresholds when selecting people with type 2 diabetes for antihypertensive therapy," they concluded. 

Reference:

Nazarzadeh M, Bidel Z, Canoy D, et al. Blood pressure-lowering treatment for prevention of major cardiovascular diseases in people with and without type 2 diabetes: an individual patient-level data meta-analysis. Lancet Diabetes Endocrinol. 2022;Epub ahead of print.