LOWER BP IS NOT ALWAYS BETTER

November 22, 2010 — Diastolic blood pressure (BP) of less than 70 mm Hg in patients with type 2 diabetes is linked to increased cardiovascular risk, even when systolic BP is in guideline-recommended target ranges, according to the results of a study reported online ahead of print November 8 in Diabetes Care.

"Blood pressure ranges associated with cardiovascular disease (CVD) events in advanced type 2 diabetes are not clear," write Robert J. Anderson, MD, from the VA Medical Center in Omaha, Nebraska, and colleagues. "Our objective was to determine whether baseline and follow-up (On-Study) systolic BP (SBP), diastolic DBP, and SBP combined with DBP predict CVD events in the Veterans Affairs Diabetes Trial (VADT)."

In the Veterans Affairs Diabetes Trial, 1791 participants with hypertension in a standard glycemic treatment group and an intensive glycemic treatment group were assigned to stepped treatment with the goal of maintaining BP below 130/80 mm Hg. The investigators determined associations of BP levels of all participants at baseline and On-Study with cardiovascular risk, using a main study endpoint of the time from randomization to the first event of myocardial infarction, stroke, congestive heart failure, surgery for vascular disease, inoperable coronary disease, amputation for ischemic gangrene, or death from cardiovascular disease.

Isolated systolic BP of at least 140 mm Hg was associated with cardiovascular risk both at baseline (hazard ratio [HR], 1.508; P < .001) and On-Study (HR, 1.469; P = .002). Diastolic BP of less than 70 mm Hg was also associated with increased cardiovascular risk at baseline (HR, 1.482; P < .001) and On-Study (HR, 1.491; P < .001).

When combined BP categories were analyzed, the risk for cardiovascular events was increased for a systolic BP of 140 mm Hg or more with a diastolic BP of less than 70 mm Hg at baseline (HR, 1.785; P = .03) as well as On-Study (HR, 2.042; P = .003), and for nearly all systolic BP readings with diastolic BP of less than 70 mm Hg.

"Increased risk of CVD events with SBP≥140 mmHg emphasizes the urgency for treatment of systolic hypertension," the study authors write. "Increased risk with DBP<70 mmHg, even when combined with SBP in guideline-recommended target ranges, supports a new finding in patients with type 2 diabetes. The results emphasize that DBP<70 mmHg in these patients was associated with elevated CVD risk and may best be avoided."

Limitations of this study include lack of randomization to BP control groups or BP treatment, lack of generalizability to younger individuals and women, low statistical power in the higher BP categories, and the confounding treatment effect of BP control during the study. In addition, this analysis did not examine the effects of lowering BP.

"A possible negative effect of antihypertensive treatments that excessively lower DBP must be considered," the study authors write. "Future research questions include whether BP control changed outcomes for individual patients in higher risk SBP or DBP categories. We also plan to investigate the potential associations of these high risk BP categories with microvascular events."

This study was supported by the VA Cooperative Studies Program, Department of Veterans Affairs Office of Research and Development, with additional support from the American Diabetes Association and the National Eye Institute of the National Institutes of Health. GlaxoSmithKline, Novo Nordisk, Roche Diagnostics, Sanofi-Aventis, Amylin, and Kos Pharmaceuticals provided pharmaceutical and other supplies and financial assistance.

Some of the study authors have disclosed various financial relationships with Roche Pharmaceuticals, the American Diabetes Association, Aventis, and/or Novo Nordisk.

Diabetes Care. Published online November 8, 2010.