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

July 25, 2014

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 HbA1c.

Given those findings and previous research, "it is speculated that there was a synergistic effect between the HbA1c 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, HbA1c, 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 HbA1c of at least 9%. That was sharply higher than the 1.58 for those with HbA1c <9% (p=0.01 for interaction). An HbA1c cut point of 8.5% didn't materially change the result (p=0.02 for interaction).

Also, in those with HbA1c ≥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 HbA1c 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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