Dietary Sodium Intake and Incidence of Diabetes Complications in Japanese Patients with Type 2 Diabetes: Analysis of the Japan Diabetes Complications Study (JDCS)

Context: Many guidelines recommend that patients with type 2 diabetes should reduce their dietary sodium intake. However, the relationship between dietary sodium intake and incidence of diabetic complications in patients with type 2 diabetes has not been explored. Objective: Our objective was to investigate the relationship between dietary sodium intake and incidence of diabetes complications. Participants: The study was of a nationwide cohort of patients with type 2 diabetes aged 40 to 70 years with hemoglobin A1c (HbA1c) >= 6.5%. Main Outcome Measures: After excluding nonresponders to a dietary survey, 1588 patients were analyzed. Baseline dietary intake was assessed by the Food Frequency Questionnaire based on food groups. Primary outcomes were times to cardiovascular disease (CVD), overt nephropathy, diabetic retinopathy, and all-cause mortality. Results: Mean daily dietary sodium intake in quartiles ranged from 2.8 to 5.9 g. After adjustment for confounders, hazard ratios for CVD in patients in the second, third, and fourth quartiles of sodium intake compared with the first quartile were 1.70 (95% confidence interval, 0.98-2.94), 1.47 (0.82-2.62), and 2.07 (1.21-3.90), respectively (trend P < .01). In addition, among patients who had HbA1c >= 9.0%, the hazard ratio for CVD in patients in the top vs bottom quartile of sodium in take was dramatically elevated compared with patients with HbA1c <9.0% (1.16 [0.56-2.39] and 9.91 [2.66-36.87], interaction P < .01). Overt nephropathy, diabetic retinopathy, and all-cause mortality were not significantly associated with sodium intake. Conclusions: Findings suggested that high dietary sodium intake is associated with elevated incidence of CVD in patients with type 2 diabetes and that there is a synergistic effect between HbA1c values and dietary sodium intake for the development of CVD.