Thermoregulatory sudomotor dysfunction and diabetic neuropathy develop in parallel in at-risk feet

Aims To establish the longitudinal relationship of foot complications to neuropathy based on a 4-year follow-up of diabetic patients stratified by sudomotor dysfunctions. Methods One hundred and nineteen Type 2 diabetic patients and 36 non-diabetic subjects were initially registered in the prospective cohort study. Plantar skin temperature and sympathetic skin response (SSR) were used to monitor sympathetic mediated thermoregulation and sudomotor function. Peripheral somatic and central autonomic functions were studied using clinical, nerve conduction and cardiovascular reflex tests. At enrolment, the diabetic patients were classified into one of three groups by the progressive stages of sudomotor dysfunction: SSR+ (SSR present; 49 patients), SSR- (SSR absent; 41 patients) and at-risk group (SSR absent but with cracked skin involving partial thickness of the dermis; 29 patients). Results The at-risk group had 13.4 times (95% confidence interval 1.4-125.7) higher plantar ulceration rates than the other two patient groups during the 4 years. Skin temperature elevation occurred in parallel with development of foot sweating problems. There were no significant differences between the three patient groups in the ratios of abnormal heart rate variation, orthostatic test and clinical neuropathy score at follow-up. After 4 years of follow-up, nerve conduction abnormalities were more frequent in the at-risk and SSR- groups than in the SSR+ group. Conclusions Early deterioration of small sympathetic fibres could not be quantified accurately by the clinical, somatic and autonomic tests. Assessing skin integrity and sudomotor function in at-risk individuals identifies early peripheral sympathetic neuropathy, even if the patients have no overt clinical symptoms.