AUTONOMIC FUNCTION IN CHILDREN WITH TYPE-1 DIABETES-MELLITUS

We investigated autonomic function in 58 children and young adults wit h Type 1 diabetes mellitus (aged 7-22 years, duration from 3 to 18, 8. 6+/-3.4 years) and in 74 healthy controls (6-21 years) using power spe ctral analysis of blood pressure and heart rate in addition to convent ional standard autonomic function tests: deep breathing, the Valsalva manoeuvre, and a standing test. None of the diabetic patients were sym ptomatic. Reproducibility of the tests was assessed by determining the coefficient of variation in 9 controls (7.8-37.7 %). Thirteen per cen t of the subjects had difficulty in adequately performing the Valsalva manoeuvre. After adjustment for age, sex, body mass index, and respir atory frequency, results of the Valsalva manoeuvre and deep breathing were not different between patients and controls and there was no sign ificant postural reduction in systolic blood pressure (greater than or equal to 20 mmHg) in the patients. Heart rate variation in the supine position during natural breathing was low in patients, although power spectral analysis of heart rate variation did not show a significant decrease in the power density in the high and the low frequency in pat ients compared to healthy controls. Beat-to-beat blood pressure fluctu ation was significantly lower in patients and correlated with metaboli c control (mean annual haemoglobin A(1c)), but not with disease durati on and was abnormal in 7 diabetic children (12 %). In contrast, tests of vagal activity were not impaired in the patients in this age range. We concluded that vagal involvement in Type 1 diabetic patients deter mined by spectral analysis of R-R intervals in addition to conventiona l tests is uncommon, but that beat-to-beat blood pressure variation wa s more likely to be affected. (C) 1998 John Wiley & Sons, Ltd.