Spotlight on blood pressure control

Intensive blood pressure control may increase diabetic patients' risk of stroke or coronary heart disease, a group of researchers recently concluded in two separate publications.

Both findings were based on a prospective cohort study of 17,536 black and 12,618 white patients with diabetes (many low-income) treated in the Louisiana State University Hospital System. Patients had their blood pressure measured upon entering the study and occasionally during follow-up, which lasted for a mean of about six years. For both stroke and new diagnosis of coronary heart disease (CHD) and for both black and white patients, the study found a U-shaped association—a higher risk of disease associated with both low and high blood pressure.

In the first analysis, published by Diabetes Care on May 20, the hazard ratios for CHD (with a reference group of 130-139/80-90 mm Hg) for black patients were 1.73 for blood pressure below 110/65 mm Hg, 1.16 for blood pressure of 110-119/65-69 mm Hg, 1.04 for blood pressure of 120-129/70-80 mm Hg, 1.06 for blood pressure of 140-159/90-100 mm Hg, and 1.11 for a blood pressure of 160/100 mm Hg or higher. The respective hazard ratios for white patients were 1.60, 1.27, 1.08, 0.95 and 0.99. This U-shaped association was present in all younger patients but changed to an inverse association in patients 60 and over.

In the stroke analysis, published by the Journal of Clinical Endocrinology and Metabolism on May 28, the reference group was 120-129/70-80 mm Hg and hazard ratios for stroke in black patients were 1.88 for blood pressure less than 110/65 mm Hg, 1.05 for a blood pressure of 110-119/65-69 mm Hg, 1.05 for a blood pressure of 130-139/80-90 mm Hg, 1.12 for a blood pressure of 140-159/90-100 mm Hg, and 1.47 for a blood pressure of 160/100 mm Hg or higher. The respective hazard ratios for white patients were 1.42, 1.22, 0.88, 1.02 and 1.28.

The researchers could not determine the cause of these U-shaped associations, but they concluded that intensive blood pressure control may increase risk for CHD and stroke. For CHD prevention in diabetic patients, “it might be advisable to maintain blood pressure between 130-139 and 80-89 mmHg and to recommend less intense goals to elderly patients than to younger ones,” they wrote. In the stroke study, they concluded that a blood pressure target of less than 130/80 mm Hg “may provide cerebrovascular protection,” although they added that for patients at high risk of a cerebrovascular event, maintaining blood pressure in the range of 120-129/70-79 mm Hg may be appropriate.