No Difference in Small or Large Nerve Fiber Function Between Individuals With Normal Glucose Tolerance and Impaired Glucose Tolerance

OBJECTIVE To assess small and large nerve fiber function in people with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and type 2 diabetes (T2D). RESEARCH DESIGN AND METHODS Participants were recruited consecutively from a population-based cohort: NGT (n = 39), IGT (n = 29), and T2D (n = 51). Electrophysiological measures included nerve conduction studies and thermal thresholds. Intraepidermal nerve fiber density (IENFD) in skin biopsies was calculated. RESULTS There was no difference between IGT and NGT in sural nerve conduction, IENFD, and thermal thresholds. IENFD was significantly lower in T2D (median = 2.8 fibers/mm [interquartile range 1.1-4.7 fibers/mm]) than NGT individuals (4.5 fibers/mm [3.4-6.1 fibers/mm]; P < 0.05). T2D participants had poorer nerve conduction and higher heat thresholds than NGT and IGT. CONCLUSIONS Large and small nerve function in people with IGT did not differ from those with NGT. Our finding does not support the existence of neuropathy in a prediabetic stage.