Systolic BP <130 mm Hg and proteinuria confer higher death risk on diabetics

Patients with type 2 diabetes who had proteinuria and systolic blood pressure (BP) less than 130 mm Hg had a higher risk of cardiovascular and total mortality than those with higher blood pressure and no proteinuria, a study found.

Researchers prospectively followed 881 Finnish patients with type 2 diabetes, aged 45 to 64 years, for 18 years. Patients were excluded if they had type 1 diabetes, had possible or definite stroke or myocardial infarction, or had lower-extremity amputation at baseline examination. They were categorized into four groups based on systolic BP at baseline: <130 mm Hg, 130-139 mm Hg, 140-159 mm Hg, and ≥160 mm Hg. They were then stratified as having no proteinuria (≤150 mg/L) or borderline/clinical proteinuria (>150 mg/L). Study endpoints were total mortality, cardiovascular disease (CVD) mortality and coronary heart disease (CHD) mortality. Researchers used a Cox proportional hazards model to evaluate the effect of systolic BP in the different proteinuria groups on mortality, using the <130 mm Hg group as the reference. Results were published online August 24 by the Journal of General Internal Medicine.

Sixty-nine percent (n=607) of patients died during follow-up, including 44.8% (n=395) from CVD. There was a statistically significant interaction between proteinuria and baseline systolic BP (P=0.01) for total mortality as well as for CVD mortality (P=0.05). The interaction for CHD mortality wasn't significant. After adjustment for confounders, patients with proteinuria and systolic BP <130 mm Hg had about twice the risk of total and CVD mortality as those with BP between 130 and 139 mm Hg (P<0.05), and about 1.6 times greater total and CVD mortality as those with systolic BP between 140 and 159 mm Hg. CVD mortality was also 1.6 times higher (P<0.05) in those with systolic BP <130 mm Hg versus those with systolic BP ≥160 mm Hg. In patients without proteinuria, a systolic BP <130 mm Hg was associated with a statistically nonsignificant decrease in total and CVD mortality.

In diabetic patients with proteinuria, systolic BP below 130 mm Hg may be a marker of underlying disease, the authors wrote. The results suggest “it might be justifiable to recommend higher systolic BP targets for patients with type 2 diabetes and proteinuria compared to those without proteinuria,” they wrote. Limitations that affect the generalizability of this study include that the baseline exam occurred from 1982-1984, blood pressure was only obtained at baseline with no follow-up, patients' baseline hemoglobin A1c was 9.9%, and there was no information about what antihypertensives (including ACE inhibitors) were taken during the study.