Altered blood pressure during sleep in normotensive subjects with type I diabetes

This study was designed to examine the circadian pattern of blood pressure in children and young adults with type I diabetes who were completely normotensive by standard criteria. Forty-five patients and the same number of age- and sex-matched control subjects were studied. In diabetic children of 10-14 years of age, the nocturnal fall in systolic and diastolic blood pressures was intact In diabetics of 15-20 years of age, the fall in systolic blood pressure was blunted; in diabetics of 21-37 years of age, the fall in both systolic and diastolic blood pressures during sleep was blunted. When data from all diabetic subjects were pooled and analyzed in a multiple linear regression model, mean blood pressure during sleep correlated best with urinary albumin excretion (r=0.60). On the basis of this finding, we subdivided our patients into two groups: a microalbuminuric group (urinary albumin excretion >30 mg per 24 hours; mean, 160.3±29.7; n = 11) and a normoalbuminuric group (urinary albumin excretion <30 mg per 24 hours; mean, 6.6±6.5; n =34). Both systolic and diastolic blood pressures during sleep were higher in microalbuminuric (121.1±3.3 and 69.3±2.5 mm Hg, respectively) than in normoalbuminuric diabetics (114.2±1.8 and 60.1±1.2 mm Hg, p<0.05) or control subjects (113.3±1.2 and 60.1±1.2 mm Hg, p<0.05). Although most microalbuminuric patients (nine of 11) had a blunted fall in blood pressure during sleep, this alteration was also seen in normoalbuminuric subjects (14 of 34 patients). We conclude that in many "normotensive" patients with type I diabetes, the physiological nocturnal fall in blood pressure is blunted. This abnormality can antedate the development of microalbuminuria, suggesting that it may prove to be a sensitive marker for renal disease and eventual progression to overt hypertension.