Noninvasive Evaluation of Neural Impairment in Subjects With Impaired Glucose Tolerance

OBJECTIVE—To evaluate neural dysfunction in subjects with impaired glucose tolerance (IGT). RESEARCH DESIGN AND METHODS—For this study, 46 subjects with IGT and 45 healthy volunteers underwent detailed neurological assessment. Cardiovascular autonomic function was assessed by standard cardiovascular reflex tests, and heart rate variability was characterized by the triangle index. Sensory nerve function was assessed using Neurometer (for current perception threshold) and Medoc devices. Peak plantar pressure was measured by dynamic pedobarography, and symptoms were graded using the neuropathy total symptom score. RESULTS—Subjects with IGT had significantly greater abnormalities detected by four of five cardiovascular reflex tests and greater heart rate variability characterized by the triangle index. They had a higher frequency of both hyperesthesia and hypoesthesia as detected by current perception threshold testing at 5 Hz, as well as increased heat detection thresholds. CONCLUSIONS—This study provides evidence that subclinical neural dysfunction is present in subjects with IGT and can be detected noninvasively. Cardiovascular autonomic neuropathy may contribute to increased cardiovascular risk in IGT subjects.