Dysfunction of the autonomic nervous system is reported to occur at an incidence of 20% to 40% in diabetes. The clinical symptoms include orthostatic hypotension, vomiting, diarrhea, bladder dysfunction, male impotence, sweating, etc. Two simple noninvasive tests, sympathetic skin response (SSR) and R-R interval variation (RRIV), were used to assess autonomic functions. We performed SSR and RRIV on the diabetic patients and controls. The patients were classified into 4 groups (group I: without peripheral neuropathy or dysautonomia, group II: with dysautonomia only, group III: with peripheral neuropathy only, group IV: with both peripheral neuropathy and dysautonomia). We also tried to correlate their clinical dysautonomic symptoms and the results of nerve conduction studies (NCS) and of SSR and RRIV.

The subjects of this study were 82 diabetic patients, 20 to 73 years old with the mean age of 53, and 12 controls.

Latency, amplitude, and loss of SSR all showed a significant difference in relation to the dysautonomic symptoms. The loss of SSR in the foot showed a remarkable difference in group I.

In groups III and IV, three RRIVs (Valsalva ratio, E:I ratio, 30 : 15 ratio) showed a significant decrease compared with the control group, and in group II, only the 30:15 ratio showed a statistically significant decrease.

In conclusion, the changes in SSR and RRIV were significantly associated with the dysautonomia. Among these, loss of SSR in the foot and decrease in the 30 : 15 ratio were useful parameters for early detection of diabetic autonomic neuropathy without peripheral neuropathy.