Impaired Distal Thermoregulation in Diabetes and Diabetic Polyneuropathy

Abstract

Objective: To determine how thermoregulation of the feet is affected by diabetes and diabetic polyneuropathy (DP) in both wakefulness and sleep.

Research Design and Methods: Normal subjects, diabetic subjects without neuropathy, diabetic subjects with small fiber DP, and those with advanced DP, were categorized based on neurological examination, nerve conduction studies, and quantitative sensory testing. Subjects underwent foot temperature monitoring using an iButton® device attached to the foot and a second iButton® for recording of ambient temperature. Socks and footwear were standardized, and subjects maintained an activity diary. Data was collected over a 32-hour period and analyzed.

Results: 39 normal subjects, 28 patients with diabetes but without DP, 14 patients with isolated small fiber DP, and 27 patients with more advanced DP participated. No consistent differences in foot temperature regulation between the four groups were identified during wakefulness. During sleep, however, multiple metrics revealed significant abnormalities in the diabetic patients. These included reduced mean foot temperature (p < 0.001), reduced maximal temperature (p < 0.001), increased rate of cooling (< 0.001), as well as increased frequency of variation (p = 0.005), supporting that patients with DP and even those with only diabetes but no DP have impaired nocturnal thermoregulation.

Conclusion: Nocturnal foot thermoregulation is impaired in patients with diabetes and DP. Since neurons are highly temperature sensitive and since foot warming is part of the normal biology of sleep onset and maintenance, these findings suggest new, potentially treatable mechanisms of diabetes-associated nocturnal pain and sleep disturbance.