Ultradian oscillations in cranial thermoregulation and electroencephalographic slow-wave activity during sleep are abnormal in humans with annual winter depression

The level of core body, and presumably brain temperature during sleep varie s with clinical state in patients with seasonal affective disorder (SAD), b ecoming elevated during winter depression and lowered during clinical remis sion induced by either light treatment or summer. During sleep, brain tempe ratures are in part determined by the level of brain cooling activity, whic h may be reflected by facial skin temperatures. In many animals, the level of brain cooling activity oscillates across the NREM-REM sleep cycle. Facia l skin temperatures during sleep in patients with winter depression are abn ormally low and uncorrelated with octal temperatures, although their relati onship to EEG-defined sleep stages remains unknown. We therefore measured t he sleep EEG, fore body and facial skin temperatures in 23 patients with wi nter depression and 23 healthy controls, and tested the hypothesis that ult radian oscillations in facial skin temperatures exist in humans and are abn ormal in patients with winter depression. We found that facial skin tempera tures oscillated significantly across the NREM-REM sleep cycle, and were ag ain significantly lower and uncorrelated with rectal temperatures in patien ts with winter depression Mean slow-wave activity and NREM episode duration were significantly greater in patients with winter depression, whereas the intraepisodic dynamics of stow-wave activity were normal in patients with winter depression. These results suggest that brain cooling activity oscill ates in an ultradian manner during sleep in humans and is reduced during wi nter depression, and provide additional support for the hypothesis that bra in temperatures are elevated during winter depression. (C) 2000 Elsevier Sc ience B.V. All rights reserved.