[BMJ] In patients with new diabetes, blood pressure below 130/80 mm Hg not associated with reduced risk of all-cause mortality

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There have been many studies assessing the role of blood pressure (BP) control and mortality in diabetes – the United Kingdom Prospective Diabetes Study (UKPDS) and Hypertension Optimal Treatment (HOT) were two of the biggest to show reductions in cardiovascular outcomes in the groups receiving tight control of blood pressure and diabetes. In the clinic – generally the lower the blood pressure in diabetics the better – which has led to aggressive BP control in diabetics. However, the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial did not show further cardiovascular benefits of antihypertensive therapy through reducing systolic blood pressure below 130 mm Hg in people with diabetes. The data for lower BP in diabetics, particularly newly diagnosed patients, is uncertain.

Just published in BMJ, this retrospective cohort study involved 126,092 adult patients adults with a new diagnosis of type 2 diabetes. The authors followed the patients for the primary outcome of all-cause mortality for a median length of 3.5 years. During this time, 25495 deaths occurred (20.2%). In people with cardiovascular disease and tight control of systolic (<130 mm Hg) and diastolic (<80 mm Hg) blood pressure was not associated with improved survival, after adjustment for baseline characteristics.

Another interesting result, which has been hinted at in previous epidemiological studies, was that low blood pressure was associated with an increased risk of all-cause mortality. As compared those patients with a systolic BP at 130-139 mm Hg, the hazard ratio of all-cause mortality was 2.79 (95% confidence interval 1.74 to 4.48, P<0.001) for systolic blood pressure at 110 mm Hg. This relationship holds true for those patients with low diastolic BP (70-74 mm Hg or <70mm Hg) when compared with patients who received usual control of diastolic blood pressure (80-84 mm Hg) – the hazard ratios were 1.32 (1.02 to 1.78, P=0.04) and 1.89 (1.40 to 2.56, P<0.001), respectively.

These relationship held true for people with and without cardiovascular disease.

In Sum: This study has the typical limitations of any retrospective cohort, and although causality cannot be confirmed from these data, the results do suggest that it may be beneficial to maintain blood pressures in the 130-139/80-85 mm Hg as opposed to the current guidelines pushing aggressive lowering.

Click here to read the article in the British Medical Journal [BMJ] database.

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