Do chronic primary insomniacs have impaired heat loss when attempting sleep?

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2006-04, Vol.290 (4), p.R1115-R1121
• Main Authors: Gradisar, Michael, Lack, Leon, Wright, Helen, Harris, Jodie, Brooks, Amber
• Format: Article
• Language: English
• Subjects: Adult; Body Temperature - physiology; Case-Control Studies; Circadian Rhythm; Electroencephalography; Female; Hot Temperature; Humans; Male; Middle Aged; Polysomnography; Skin Temperature - physiology; Sleep Initiation and Maintenance Disorders - physiopathology; Wakefulness - physiology
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00266.2005

Flinders University Sleep Research Laboratory, School of Psychology, Flinders University, Adelaide, South Australia Submitted 14 April 2005 ; accepted in final form 22 November 2005 For good sleepers, distal skin temperatures (e.g., hands and feet) have been shown to increase when sleep is attempted. This process is said to reflect the body’s action to lose heat from the core via the periphery. However, little is known regarding whether the same process occurs for insomniacs. It would be expected that insomniacs would have restricted heat loss due to anxiety when attempting sleep. The present study compared the finger skin temperature changes when sleep was attempted for 11 chronic primary insomniacs [mean age = 40.0 years (SD 13.3)] and 8 good sleepers [mean age = 38.6 years (SD 13.2)] in a 26-h constant routine protocol with the inclusion of multiple-sleep latency tests. Contrary to predictions, insomniacs demonstrated increases in finger skin temperature when attempting sleep that were significantly greater than those in good sleepers ( P = 0.001), even though there was no significant differences in baseline finger temperature ( P = 0.25). These significant increases occurred despite insomniacs reporting significantly greater sleep anticipatory anxiety ( P < 0.0008). Interestingly, the core body temperature mesor of insomniacs (37.0 ± 0.2°C) was significantly higher than good sleepers (36.8 ± 0.2°C; P = 0.03). Whether insomniacs could have impaired heat loss that is masked by elevated heat production is discussed. finger temperature; core body temperature Address for reprint requests and other correspondence: M. Gradisar, Flinders Univ., School of Psychology, GPO Box 2100, Adelaide, S.A., Australia (e-mail: michael.gradisar{at}flinders.edu.au )