Prospective evaluation of autonomic dysfunction in aggressive management of diabetic microangiopathy

Twenty-six type I diabetic nephropathy patients in a rigorous schedule for glucose control to preserve kidney function were studied to determine autonomic functional changes during 18 months. Intercurrent and nonrelated acute illness, withdrawal from the study for personal reasons, or failure to undergo testing on schedule resulted in complete data at 1 year for 26 of the original 41 patients enrolled, 24 patients completing a further 6 months. Glycohemoglobin A1c dropped for the total group from 9.0 to 7.9 at 6 months, 8.0 at 12 months, and 8.1 at 18 months (P< .01). Autonomic function tests revealed baseline results that were below the anticipated normals for age in 38% to 56% of patients. Timed ventilatory heart rate variations measured for the total group were 1.11, 1.13, 1.10, and 1.09 (normal ≥1.20). Valsalva heart rate variations for the total group were 1.27, 1.30, 1.255, and 1.35 (normal ≥1.50). Assumption of upright posture-related heart rate variations for the total group were 1.10, 1.07, 1.07, and 1.06 (normal ≥1.20). Mean arterial pressure day/night ratios for the total group were 1.04, 1.05, 1.05, and 1.08 (normal ≥1.10). Group analysis based on differences in insulin treatment programs, levels of blood pressure, and levels of renal function revealed no significant differences from the total group or companion groups during 18 months. Patients with a glycohemoglobin A1c of <8.0% were more likely to normalize mean arterial pressure day/night ratios than those with glycohemoglobin A1c ≥8.0%. We conclude that aggressive glucose control in diabetic patients with proteinuria for a period of 18 months resulted in a reproducible pattern of autonomic function tests during that period of time with neither worsening nor improvement. The restoration of day/night mean arterial pressure variation in a minority of patients should be studied with a larger cohort.