Sudomotor dysfunction as a measure of small fiber neuropathy in type 1 diabetes

Background: This study evaluated whether measuring the electrochemical skin conductance (ESC), as an indirect measure of sudomotor function, may be also a reliable surrogate for early cardiovascular autonomic neuropathy (CAN).

Methods: Longitudinal study included 37 type 1 diabetes (T1D) subjects (mean age 38±13years, duration 15±7years, HbA1c 7.9±1.1%, no known complications at baseline), and 40 age-matched healthy control (HC) subjects. Mean hands ESC (ESChands) and feet (ESCfeet) were measured with the SUDOSCAN (Impeto Medical, France). CAN was assessed with heart rate variability (HRV) studies (ANSAR Inc., PA), cardiovascular autonomic reflex tests (deep-breathing, Valsalva, postural test), and positron emission tomography with sympathetic analogue [11C]meta-hydroxyephedrine. Associations between measures of CAN and ESC were estimated using Spearman correlations. Longitudinal changes were analyzed using paired t-test.

Results: At baseline, there were no differences between T1D and HC in ESChands (69±14 vs. 69±13μS; P=0.84) or ESCfeet (82±8 vs. 78±9μS; P=0.12), while some indices of HRV and Valsalva ratio were significantly lower in T1D vs. HC. T1D subjects experienced a significant decline in both ESChands and ESCfeet at 12months (mean change -7.2±11.6µS, P=0.0006; -2.8±7.3µS, P=0.023 respectively). No significant correlations were consistently found between ESC and measures of CAN at baseline or at 12months.

Conclusion: Comparing patients with T1D to controls, no differences in ESC were observed at baseline. The associations between ESC and established measures of CAN were inconsistent, which does not support ESC as a reliable surrogate for CAN. While both hands and feet ESC declined over time, the significance of this finding is unclear and warrants further reliability testing.