A new large scale study found that depending on baseline systolic blood pressure (SBP) level, the use of antihypertensive medication led to different outcomes in patients with diabetes. Researchers, from Umeå University in Sweden, found that the risk of mortality and cardiovascular morbidity was lowered for patients whose baseline SBP was greater than 140 mmHg, while the same treatment was linked to an increased risk of cardiovascular death for those with SBP below 140 mmHg. These results contrast with a previous study which suggested significant benefits in diabetes patients when blood pressure was lowered to below 130 mmHg.
The researchers conducted a meta-analysis of 49 randomized controlled trials which included a total of 73,738 diabetes patients, most of whom had type 2 diabetes. Specifically, for patients with baseline SBP greater than 150 mmHg, antihypertensive treatment reduced the risk of all cause mortality (relative risk 0.89, 95% confidence interval 0.80 to 0.99), cardiovascular mortality (0.75, 0.57 to 0.99), myocardial infarction (0.74, 0.63 to 0.87), stroke (0.77, 0.65 to 0.91), and end stage renal disease (0.82, 0.71 to 0.94).
Patients whose SBP was between 140 mmHg and 150 mmHg, also showed a marked reduced risk, but not the same level as those over 150 mmHg; all cause mortality (0.87, 0.78 to 0.98), myocardial infarction (0.84, 0.76 to 0.93), and heart failure (0.80, 0.66 to 0.97).
In cases were baseline SBP was less than 140 mmHg, however, additional antihypertensive treatment increased the risk of cardiovascular mortality (1.15, 1.00 to 1.32), with a tendency towards an increased risk of all cause mortality (1.05, 0.95 to 1.16), this was backed up by metaregression analysis. Baseline and attained SBP data were stratified for meta-analysis to assess the effect of treatment at different pressure level groups.
The interaction between blood pressure and treatment effect in the study is reproducible across exposure variables and outcomes, indicating a robust dose-response relation. The authors assert their research shows not only the absolute, but also the relative benefit of blood pressure lowering is lessened when the individual patient has a lower baseline. “This review strongly supports blood pressure treatment in people with diabetes mellitus if SBP is more than 140 mmHg. If SBP is already less than 140 mm Hg, however, adding additional agents might be harmful,” the authors sign off.
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