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Nocturnal Foot Heat Regulation Impaired in Diabetes

Regulation of foot temperature in patients with diabetes, with or without diabetic polyneuropathy, is significantly impaired during sleep, according to a recently published study…

Dr. Seward Rutkove of Beth Israel Deaconess Medical Center in Boston stated that, “Patients with diabetic neuropathy often have sleep problems…. We’ve shown that they also have abnormal foot temperature. Since others have shown that good sleep depends on normal foot temperature, measures to normalize foot temperature (for example, external foot warming) may improve sleep in diabetic patients.”

“The normal homeostatic mechanisms to maintain foot temperature are disturbed in diabetes and diabetic neuropathy,” Dr. Rutkove added. “This impairment in foot temperature may allow feet to become consistently cooler, possibly predisposing to injury and worsening of diabetic neuropathy” and creating a kind of vicious cycle.

The study involved 4 groups: 14 patients with diabetic small-fiber polyneuropathy, 27 with more severe diabetic polyneuropathy with large-fiber involvement, 28 diabetic patients without polyneuropathy, and 39 healthy controls.

Each participant underwent at least 32 hours of monitoring of both foot temperature and ambient temperature, in each case using an iButton temperature logger, one taped just above the first and second toes and the other worn on a key ring affixed to external clothing.

Foot activity was logged using an ankle-worn actigraphy monitor, and participants also maintained paper activity diaries for the period of the study.

The researchers’ hypothesis that differences in ambulatory (daytime) foot thermoregulation might serve as a noninvasive test for small-fiber diabetic polyneuropathy was not proven. No parameters were found that distinguished such patients from other participants while awake.

During sleep, however, several metrics were consistently and significantly different between patients with diabetes and healthy controls. These included reduced mean foot temperature (P < 0.001), reduced maximal temperature (P < 0.001), increased rate of cooling (P < 0.001) and increased frequency of temperature variation (P < 0.005).

“These findings suggest new potentially treatable mechanisms of diabetes-associated nocturnal pain and sleep disturbance,” the researchers conclude.

Diabetes Care 2009;32:671-676.