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 (24hUNa). The predictors of all-cause and cardiovascular mortality were determined by Cox regression and competing risk modeling, respectively.
RESULTS The mean baseline 24hUNa 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 24hUNa, 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, 24hUNa 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 sodium excretion 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.
- Received September 6, 2010.
- Accepted December 30, 2010.
- © 2011 by the American Diabetes Association.
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