Systolic blood pressure in diabetes: Should recommended targets be lowered?

Hypertension guidelines are reviewing their recommended target for systolic blood pressure in diabetes, aiming for below 130 mmHg instead of below 140 mmHg. There is a relative lack of clinical trial data supporting this potential target. Many observational data sets have suggested a J-shaped association between blood pressure and cardiovascular events, although such observations are always limited by confounding comorbidities.

The objective of the study by Adamsson Eryd and colleagues (summarised alongside) was to compare the risk associated with systolic blood pressure that meets current recommendations (that is, below 140 mmHg) with the risk associated with lower levels in patients who have type 2 diabetes and no previous cardiovascular disease. This was a Swedish population-based record-linked cohort study from nationwide clinical registries between 2006 and 2012, with a mean follow-up of 5 years. The study included 187106 patients who had had type 2 diabetes for at least a year, were aged 75 years or younger, and had no previous cardiovascular or other major disease.

The index date was defined as the first examination after the patient had been included in the diabetes register, with all individuals being followed from the index date until a first event, death or the end of follow-up on 31 December 2013.

The group of patients with the lowest systolic blood pressure (110–119 mmHg) had a significantly lower risk of non-fatal acute myocardial infarction (adjusted hazard ratio, 0.76; 95% confidence interval, 0.64–0.91; P=0.003), total acute myocardial infarction (0.85; 0.72–0.99; P=0.04), non-fatal cardiovascular disease (0.82; 0.72–0.93; P=0.002), total cardiovascular disease (0.88; 0.79–0.99; P=0.04), and non-fatal coronary heart disease (0.88; 0.78–0.99; P=0.03) compared with the reference group (130–139 mmHg). Furthermore, there was no indication of a J-shaped relation between systolic blood pressure and any of the endpoints, with the exceptions of heart failure and total mortality. A secondary analysis illustrated a J-shaped association between systolic blood pressure and cardiovascular events in patients with established cardiovascular disease, with an apparent risk inflection at a systolic blood pressure <130 mmHg.

This study supports, therefore, the potential benefit of reducing systolic blood pressure well below 130 mmHg in people with type 2 diabetes and no established comorbidities and, as such, could inform treatment paradigms with respect to blood pressure targets in type 2 diabetes. Its main strength is the large number of participants, including patients from a nationwide diabetes register, with a high participation rate evaluating data derived from routine practice. This study did not evaluate the effect of blood pressure variations during the study period and, importantly, did not include patients >75 years of age. Thus, it cannot inform on blood pressure management in elderly patients with type 2 diabetes.

In summary, this population-based study demonstrated that systolic blood pressure levels well below currently advocated targets were associated with reduced cardiovascular risk in patients with type 2 diabetes in a primary prevention setting. Furthermore, it also highlights that any potential association between low blood pressure and increased mortality is likely to be caused by concomitant disease rather than antihypertensive treatment.

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