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.