International Health News

Blood pressure and risk of coronary heart disease in diabetics

BATON ROUGE, LOUISIANA. If one is diagnosed as having type 2 diabetes, it is quite likely that glucose lowering medication, statins and antihypertensive medication will be recommended, either to initiate or continue. The aggressive control of hypertension for diabetics and the belief that "lower is better" was based on randomized controlled trials in the 1990s. However, this has now been questioned since contrary evidence has been forthcoming. The most recent is a follow-up study of 12,600 white and 17,500 African American diabetics 30-94 years of age who were studied for 6 years. Blood pressure data was collected on average 14.6 times during follow-up. Heart disease was defined as a heart attack or unstable angina. It was found that the minimum risk occurred for the blood pressure range 130-39/80-89 mm Hg. Risk increased below this range, and for 140-159/90-99 and equal to or greater than 160, the only statistical significant result was an increased risk seen in those under 50 years of age. Plots arising from continuous modeling suggest the risk increases in general in the two higher ranges, but the data analyzed in terms of hazard ratios with confidence intervals do not support this and suggest only non-significant results, for both white and African Americans if the age is equal to or greater than 50. For the oldest group, the continuous model actually indicated an inverse association between heart disease risk and blood pressure.

The authors comment that their results are consistent with the ACCORD study where intensive blood pressure lowering below 120 mm Hg in diabetics did not produce a beneficial effect, and the INVEST study where tight control (<130 mm Hg) was not associated with improved outcome compared a control group with systolic blood pressure at 130-139 mm Hg in patients with diabetes. They also point to a recent UK study which found a U-shaped association with either systolic or diastolic blood pressure and all-cause mortality among type 2 diabetics and other studies have found an inverse association between blood pressure levels and all-cause mortality among elderly diabetic patients.

The authors suggest that there is currently no robust evidence favouring a target of a systolic of < 139 mm Hg. It is interesting that in December, 2012, the American Diabetes Association issued new clinical guidelines that included a systolic target of < 140 rather than < 130 mm Hg.

Zhao W, Katzmarzyk PT, Horswell R et al. Aggressive Blood Pressure Control Increases Coronary Heart Disease Risk Among Diabetic Patients. Diabetes Care 2013 May 20

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