Autonomic function in type I diabetes mellitus complicated by nephropathy. A cross-sectional analysis in the presymptomatic phase.

The purpose of this study was to determine the prevalence of parasympathetic and sympathetic autonomic dysfunction in long-standing type I diabetics with established nephropathy and to correlate autonomic function with cardiac risk factors. We used prospective analysis of heart rate variations to standardized testing and 24-hour blood pressure control prior to enrollment in a study utilizing various methods of intense diabetic control to prevent deterioration of kidney function. The settings were outpatient clinical research units. The patients were 42 type I diabetics with proteinuria (total urinary protein > or = 300 mg/day or urinary albumin > or = 100 mg/day) and creatinine clearance > or = 30 mL/min. Heart rate variation during respiratory cycles with change in posture from supine to upright, and during the Valsalva maneuver was recorded by a computerized method. Mean arterial blood pressure was recorded for 24 h by a computerized method. Heart rate variations in this group were abnormal during timed respiratory cycles in 26 of 40 patients (56%), during changes in posture in 15 of 40 patients (38%), and during Valsalva maneuver in 13 of 34 patients (38%) whose retinal disease permitted Valsalva testing. Blunted day/night mean arterial pressure ratios occurred in 18 of 41 (44%) patients and were more severe in men than in women (1.00 v 1.06, P < or = .05). Absence of deep tendon reflexes was associated with an increased incidence of both parasympathetic (respiratory rate variation) and sympathetic (postural rate variation) abnormalities (both P < or = .05). Loss of vibration sensation was not associated with autonomic functional abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)