DIURNAL BLOOD-PRESSURE VARIATIONS IN NORMOALBUMINURIC TYPE-1 DIABETIC-PATIENTS

Objective. To test the hypothesis that normoalbuminuric type 1 diabetic patients segregate into groups with normal and elevated ambulatory blood pressure. To evaluate diurnal variation of blood pressure assessed by individual or fixed night-time periods. Design. Cross-sectional study. Setting. Tertiary referral centre. Subjects. Inclusion criteria for type 1 diabetic patients (n = 33): normal urinary albumin excretion (UAE age < 45 < 20 mug min-1), diabetes duration less-than-or-equal-to 20 years, age 45 years. Healthy controls (n = 33) were matched for sex and age. Main outcome measure. Twenty-four hour, day-time, night-time and night/day ratio of ambulatory blood pressure. Results. Twenty-four-hour blood pressure in diabetic patients did not differ significantly from a normal distribution. The 24-h systolic blood pressure was higher in diabetic patients than in healthy controls (difference: 6 mmHg, 9 5 % confidence interval (CI) from 1 to 10 mmHg, P < 0.05), while no significant differences were found for diastolic values. The 24-h systolic blood pressure in diabetic patients with UAE above the median value (5.8 mug min-1) was higher than for those with lower UAE (difference: 7 mmHg, 9 5 % CI from 0. 5 to 1 3 mmHg, P < 0. 0 5). The night/day ratio of diastolic blood pressure based on individual informations of the night period was (mean+/-SD) 80+/-6% in diabetic patients and 78 + 8 % in controls (difference: 2 %, 9 5 % CI from - 1 to 5 %, not significant [NS]). This ratio increase significantly (P < 0. 0000 1) to 90 +/- 5 % in diabetes and to 84 +/- 7 % in controls if a fixed night period from 22.30 hours to 06.30 hours was assumed. Conclusions. It was not possible to identify a well-separated group of normoalbuminuric type 1 diabetic patients with elevated ambulatory blood pressure. Values of UAE above the median in diabetic patients are associated with higher ambulatory blood pressure. Assessment of the night/day variation from fixed time-points should be abandoned because this leads to a serious underestimation of the nocturnal reduction in blood pressure.