Abnormal thermoregulation in diabetic autonomic neuropathy.

Hypothermia has been reported to be more common in diabetic people than in nondiabetic people, and we have investigated the possibility that autonomic neuropathy may be associated with disordered thermoregulation. After an overnight fast and maintenance of normoglycemia, 12 insulin-treated diabetic patients with and 11 without neuropathy and 12 nondiabetic control subjects, all less than 55 yr, were subjected to external cooling by perfusing water at 16 degrees C through a liquid-conditioned coverall for less than or equal to 45 min. Patients with autonomic neuropathy had impaired vasoconstriction to cooling, particularly in the foot, calf, and forearm. Core temperature rose by 0.2 degrees C in control subjects and by 0.15 degrees C in patients with diabetes but no neuropathy. In contrast, group mean core temperature was unchanged in those with autonomic neuropathy and fell in 3 subjects (P less than .001). Cooling caused shivering in 6 patients with diabetic autonomic neuropathy, but not in those with neuropathy or control subjects (P less than .05). Baseline metabolic rates were similar in all three groups, but the increase after cooling was significantly greater among those who shivered (P less than .05-.02). Thus, young diabetic patients with autonomic neuropathy have impaired thermoregulation to a relatively short period of external cooling, even during metabolic stability, which may predispose to hypothermia.