Cardiovascular Autonomic Neuropathy Is Associated with Microalbuminuria in Older Patients with Type 2 Diabetes

OBJECTIVE - Cardiovascular autonomic neuropathy is associated with microalbuminuria in young and middle-aged patients with type 2 diabetes. We examined this relationship and the potential mediating role of blood pressure in older patients. RESEARCH DESIGN AND METHODS - At least two of three components of cardiovascular autonomic testing were completed by 132 patients (mean age 70 ± 5.6 years). Relative rankings on each of the components were averaged to create a summary heart rate variability (HRV) measure. The urine microalbumin-to-creatinine ratio (milligrams albumin/grams creatinine) was calculated. Blood pressure was measured at rest and by 24-h ambulatory recording. RESULTS - Urine microalbumin-to-creatinine ratio was higher in those with lower HRV (mean urine microalbumin-to-creatinine ratio 28, 56, and 191 mg/ g from the highest to lowest tertile of HRV; P < 0.0001). Resting and ambulatory blood pressure levels were negatively correlated with HRV and positively correlated with urine microalbumin-to-creatinine ratio. In multivariate analysis adjusting for age, duration of diabetes, HbA _1c, and HDL cholesterol, HRV and blood pressure were both independently associated with urine microalbumin-to-creatinine ratio, with no evidence that either mediates the effect of the other. CONCLUSIONS - Cardiovascular autonomic neuropathy and blood pressure are independently associated with microalbuminuria in older patients with type 2 diabetes.