Blood pressure does not rise before the onset of microalbuminuria in children followed from diagnosis of type 1 diabetes. Oxford Regional Prospective Study Group

Abstract

Objective: To examine whether a rise in blood pressure could be detected before the onset of microalbuminuria (MA) in a cohort of children followed from diagnosis of type 1 diabetes.

Research design and methods: The Oxford Regional Prospective Study is an incident cohort study of children with type 1 diabetes aged (mean +/- SD) 9.8 +/- 3.7 years at diagnosis. Subjects were assessed annually from diagnosis, with measurement of HbA1c, arterial blood pressure (random zero), and three urine samples for estimation of the albumin/creatinine ratio. During follow-up, 63 of 494 children developed MA at one or more annual assessments and were designated as cases for a nested case-control study. Each case was matched for sex and age at diagnosis with two normoalbuminuric control subjects. Blood pressure (BP) data were compared at corresponding years of diabetes duration.

Results: Cases with MA were similar to normoalbuminuric control subjects with respect to age and BMI, but they had higher mean HbA1c levels (mean difference 1.1%, P < 0.001). In the years before the onset of MA, the diastolic BP standard deviation score (SDS) was significantly higher than zero in cases (mean 0.49, P < 0.001) and in control subjects (0.50, P < 0.001). No difference could be detected between cases and control subjects before the onset of MA in either systolic or diastolic BP (mean difference systolic -1.2 mmHg [95% CI -4.7 to 2.7], mean difference diastolic 0.1 mmHg [-2.4 to 2.6]). However, within the cases, the onset of MA was associated with elevations in systolic and diastolic BP SDSs (F = 16.1, P < 0.001; and F = 18.0, P < 0.001). BMI, but not HbA1c, was associated with systolic and diastolic BP SDSs in the subjects with MA (F = 0.6, P = 0.4; and F = 12.3, P = 0.001). However, the association of BP with MA remained signifcant for systolic BP (P = 0.001) and for diastolic BP (P < 0.001) after adjusting for BMI.

Conclusions: A rise in systemic BP cannot be detected before the first appearance of MA in children with type 1 diabetes. BP rises concurrently with the onset of MA and is also closely related to BMI.