Dietary salt intake and mortality in patients with type 2 diabetes

Objective: Many guidelines recommend that patients with type 2 diabetesshould aim to reduce their intake of salt. However, the precise relationshipbetween dietary salt intake and mortality in patients with type 2 diabetes hasnot been previously explored. 

Research and Design Methods: Six hundredand thirty-eight patients attending a single diabetes clinic were followed in aprospective cohort study. Baseline sodium excretion was estimated from 24-hurinary collections (24hU_Na). The predictors of all-cause and cardiovascularmortality were determined by Cox regression and competing risk modeling,respectively. 

Results: The mean baseline 24hU_Na was 184 ± 73 mmol/24 h, whichremained consistent throughout the follow-up (intra individual coefficient ofvariation [CV] 23 ± 11%). Over amedian of 9.9 years, there were 175 deaths, 75(43%) of which were secondary to cardiovascular events. All-cause mortality wasinversely associated with 24hU_Na, after adjusting for other baseline risk factors(P < 0.001). For every 100 mmol rise in 24hU_Na, all-cause mortality was28%lower (95% CI 6–45%, P = 0.02). After adjusting for the competing risk ofnoncardiovascular death and other predictors, 24hU_Na was also significantlyassociated with cardiovascular mortality(sub-hazard ratio 0.65 [95% CI0.44–0.95]; P = 0.03). 

Conclusions: In patients with type 2 diabetes, lower 24-h urinary sodiumexcretion wasparadoxically associated with increased all-cause andcardiovascular mortality. Interventionalstudies are necessary to determine ifdietary salt has a causative role in determining adverseoutcomes in patientswith type 2 diabetes and the appropriateness of guidelines advocatingsaltrestriction in this setting.