Impaired diurnal cardiac autonomic function in subjects with type 2 diabetes

OBJECTIVE - To assess diurnal cardiac sympathetic and parasympathetic nerve functions in diabetic subjects with variable diabetic neuropathy, RESEARCH DESIGN AND METHODS - Frequency domain analysis of 24-h Holter ECG was done for 132 diabetic subjects (84 without any symptomatic neuropathy; 37 with only symptomatic peripheral neuropathy: 11 with symptomatic autonom ic neuropathy) and 57 normal volunteers to calculate the low frequency (LF) component representing the beta-adrenoceptor function and the high frequen cy (HF) component: representing the cardiac parasympathetic nerve function. RESULTS - Cardiac LF and HF components in diabetic subjects without periphe ral neuropathy showed values comparable to those of normal volunteers and a similar circadian rhythm, Diabetic subjects with peripheral neuropathy or autonomic neuropathy showed significantly depressed LF and HF components an d loss of the circadian rhythm of LF and HF components compared with diabet ic subjects without neuropathy Impairment of the LF component in the aftern oon could be accounted for by the duration of diabetes and elevated HbA(1c) level. Impairment of the HF component at night could be accounted for by t he duration of diabetes but not an elevated HbA(1c) level. CONCLUSIONS - These data indicated that diabetic subjects with peripheral n europathy and diabetic subjects with symptomatic autonomic neuropathy, but not diabetic subjects without neuropathy, showed a marked decrease in cardi ac sympathetic and parasympathetic nerve functions and loss of circadian rh ythm.