CV Impact of High Sodium Intake in Diabetics Rises With Diabetes Severity: Japanese Study

TOKYO, Japan — High levels of dietary sodium in people with type 2 diabetes independently corresponded to elevated risk for cardiovascular events over eight years in a prospective Japanese cohort study^[1]. The link between sodium intake and outcomes was particularly strong among those with the most poorly controlled levels of HbA_1c.

Given those findings and previous research, "it is speculated that there was a synergistic effect between the HbA_1c level and dietary sodium intake for the development of CV disease," write the authors, led by Chika Horikawa (University of Niigata Prefecture Faculty of Human Life Studies, Japan), in a report published online July 22, 2014 in the Journal of Clinical Endocrinology & Metabolism.

The group's analysis covered 1588 respondents to a diet questionnaire that was part of the nationwide Japan Diabetes Complications Study (JDCS); their mean sodium intake varied in quartiles from 2.8 g/day to 5.9 g/day. Follow-up, which was completed in 76% of the cohort, averaged eight years.

With quartiles corresponding to rising daily sodium consumption, adjusted hazard ratios (HRs) for cardiovascular events were 1.73 (p=0.05), 1.58 (p=0.12), and 2.17 (p=0.01) for quartiles 2, 3, and 4, respectively, compared with quartile 1 (p=0.02 for trend). Covariates included demographics, body-mass index, HbA_1c, diabetes duration, LDL and HDL cholesterol, triglycerides, treatment with insulin and lipid-lowering agents, smoking status, alcohol and sodium intake, caloric intake, physical-activity level, systolic blood pressure, and drugs for hypertension.

The HR for CV events in sodium-intake quartile 4 compared with quartile 1 was 16.14 among the 332 subjects with HbA_1c of at least 9%. That was sharply higher than the 1.58 for those with HbA_1c <9% (p=0.01 for interaction). An HbA_1c cut point of 8.5% didn't materially change the result (p=0.02 for interaction).

Also, in those with HbA_1c ≥9%, the adjusted HRs for CV events were 3.52, 3.75, and 9.91, respectively, for the second through fourth quartiles of sodium intake compared with the first quartile (p<0.01 for trend and for interaction). No such significant effects were seen among patients with lower HbA_1c levels.

Dietary sodium intake wasn't similarly associated with risk for overt diabetic nephropathy or diabetic retinopathy. But the authors speculate that although current salt-restriction guidelines were derived from nondiabetic populations, "dietary salt restriction as medical nutritional treatment would be useful to prevent complications of diabetes in patients with type 2 diabetes."

The authors have disclosed no relevant financial relationships.

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Cite this: CV Impact of High Sodium Intake in Diabetics Rises With Diabetes Severity: Japanese Study - Medscape - Jul 25, 2014.