Salt sensitivity in hypertensive type-1 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-1 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 (250 mmol/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.

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-1 diabetic patients compared with essential hypertensive patients.