DIABETES-MELLITUS BUT NOT IMPAIRED GLUCOSE-TOLERANCE IS ASSOCIATED WITH DYSFUNCTION IN PERIPHERAL-NERVES

To clarify whether long-term impaired glucose tolerance (IGT) is assoc iated with dysfunction of peripheral and autonomic nerves, age-matched men with IGT and diabetes mellitus were followed prospectively for 12 -15 years, when peripheral and autonomic nerve function was assessed. The patients comprised four subgroups: (1) 51 IGT subjects (duration o f IGT at least 12-15 years); (2) 35 diabetic patients, with IGT 12-15 years ago, who later developed diabetes; (3) 34 diabetic patients, dur ation of diabetes at least 12-15 years; and (4) 62 age-matched non-dia betic control subjects. Mean age of the whole study population was 61/-2 years (mean+/-SD), not different in the four groups. Peripheral ne rve function tests included nerve conduction velocities, amplitudes, d istal latencies, F-reflexes, and sensory perception thresholds for hea t, cold, and vibration. Autonomic nerve function tests included the he art rate reaction during deep breathing (expiration to inspiration rat io) and to tilt (acceleration and brake indices). Despite 12-15 years of IGT, peripheral nerve function did not differ between IGT and contr ol subjects, whereas autonomic nerve function deviated; an abnormal ex piration to inspiration ratio (a sign of vagal nerve dysfunction) was significantly more common (15/51 versus 5/62; p<0.01) in IGT than in c ontrol subjects. Diabetic patients (groups 2 and 3) showed lower condu ction velocities (in general 2-4 m s-1 lower) than IGT and control sub jects in all tested nerves. In conclusion, diabetes but not IGT, is as sociated with peripheral nerve dysfunction.