Assessment of early stage autonomic nerve dysfunction in diabetic subjects--application of power spectral analysis of heart rate variability.

To assess early stage autonomic nerve dysfunction, power spectral analyses were conducted on the consecutive RR records of healthy subjects (N/C, n = 21) and age-matched diabetic patients without neuropathy (DNN, n = 11), with peripheral neuropathy alone (DPN, n = 14), and with autonomic neuropathy (DAN, n = 13) during resting, deep breathing, and tilting. From the analyses, power spectral densities of low frequency (0.05-0.1 Hz) component (LF; msec2) and of high frequency (0.2-0.35 Hz) component (HF; msec2) were calculated as expressing sympathetic activity and parasympathetic activity, respectively. In N/C, LF and HF were 466 +/- 332 and 251 +/- 151, respectively. Deep breathing significantly (p less than 0.05 by paired t-test) increased HF to 403 +/- 305 and tilting increased LF significantly to 593 +/- 375. In diabetics as a group, both LF and HF were significantly smaller than those in N/C. DNN showed significantly smaller HFs than N/C. DPN showed a significantly smaller HF during deep breathing (135 +/- 93) and a significant smaller LF during tilting (122 +/- 119) than N/C. DAN showed a significantly smaller HF during deep breathing (49 +/- 49) and a significantly smaller LF during tilting (54 +/- 52) than DPN. Tilting increased LF significantly (p less than 0.001) in N/C but not in diabetics. Deep breathing increased HF significantly (p less than 0.001) in N/C and DNN. HF in diabetics highly correlated with known duration of diabetes. LF in diabetics did not correlate with known duration of diabetes nor level of hemoglobin A1c.(ABSTRACT TRUNCATED AT 250 WORDS)