Dietary salt intake and mortality in patients with type 2 diabetes

Abstract

OBJECTIVE - Many guidelines recommend that patients with type 2 diabetes should aim to reduce their intake of salt. However, the precise relationship between dietary salt intake and mortality in patients with type 2 diabetes has not been previously explored. RESEARCH DESIGN AND METHODS - Six hundred and thirty-eight patients attending a single diabetes clinic were followed in a prospective cohort study. Baseline sodium excretion was estimated from 24-h urinary collections (24hU Na). The predictors of all-cause and cardiovascular mortality were determined by Cox regression and competing risk modeling, respectively. RESULTS - The mean baseline 24hU Na was 184 ± 73 mmol/24 h, which remained consistent throughout the follow-up (intraindividual coefficient of variation [CV] 23 ± 11%). Over a median of 9.9 years, there were 175 deaths, 75 (43%) of which were secondary to cardiovascular events. All-cause mortality was inversely associated with 24hUNa, after adjusting for other baseline risk factors (P , 0.001). For every 100 mmol rise in 24hU Na, all-cause mortality was 28% lower (95% CI 6-45%, P = 0.02). After adjusting for the competing risk of noncardiovascular death and other predictors, 24hU Na was also significantly associated with cardiovascular mortality (sub-hazard ratio 0.65 [95% CI 0.44-0.95]; P = 0.03). CONCLUSIONS - In patients with type 2 diabetes, lower 24-h urinary sodiumexcretion was paradoxically associated with increased all-cause and cardiovascular mortality. Interventional studies are necessary to determine if dietary salt has a causative role in determining adverse outcomes in patients with type 2 diabetes and the appropriateness of guidelines advocating salt restriction in this setting. © 2011 by the American Diabetes Association.