Salt Sensitivity in Hypertensive Type-1 Diabetes Mellitus

Gerdts E, Svarstad E, Myking OL, Lund-Johansen P, and Omvik P. Salt sensitivity in hypertensive type-I diabetes mellitus. As sodium retention has been proposed as a causal factor in the development of hypertension in diabetic patients, a high incidence of salt sensitivity has been suggested. To evaluate the influence of dietary sodium intake on blood pressure, casual and 24-h blood pressure was measured in 30 hypertensive type-I diabetic patients aged 24-67 (mean 46) years while they were on habitual diet, after 6 days of low-sodium diet (50 mmol/day), and after 6 days of high-sodium diet (250mmol/day). Nine patients (30%) who increased their 24-h mean blood pressure by more than 10% when going from low- to high-sodium intake were classified as salt sensitive; the others as salt resistant. The salt sensitive group had a significantly lower urinary excretion of dopamine at baseline, and a higher diuresis and a more pronounced decrease in 24-h blood pressure during salt depletion (all p < 0.01). Low-sodium diet reduced casual and 24-h blood pressure by 4% in the total study population compared with 9% in the salt sensitive group (p < 0.01). There was no difference in glomerular filtration rate, filtration fraction, proteinuria or urinary sodium excretion between the groups. Conclusions: Sodium restriction more effectively reduces blood pressure in the salt sensitive minority of hypertensive type-1 diabetic patients irrespective of renal function. The incidence of salt sensitivity is not increased in hypertensive type-I diabetic patients compared with essential hypertensive patients.