Study objectives: The aim of this study was to test for heightened physiological activity in elderly poor sleeepers compared to good sleepers under ad lib sleep and constant wakeful conditions.

Design and setting: Subjects participated in a five-day protocol consisting of four nights of polysomnographic (PSG) and rectal temperature monitoring followed by 26 hours of continuous rectal temperature monitoring under controlled constant wakefulness.

Participants: Participants were 16 self-reported sleep maintenance insomniacs and 16 self-reported good sleeping controls over 55 years of age.

Interventions: NA.

Measurement and results: Subjects were grouped according to (1) subjective sleep status and (2) into quartiles according to amount of PSG determined wake after sleep onset (WASO). Significant group differences in temperature were observed when subjects were classified according to PSG but not subjective criteria. In the former case, subjects with the lowest (bottom quartile) compared to the highest (top quartile) amount of PSG determined WASO showed lower sleep and nighttime constant wakeful core body temperatures.

Conclusions: In the elderly, elevated core body temperature is associated with increased nocturnal wakefulness suggesting that physiological activation may underlie sleep maintenance insomnia. This was clearly significant when subjects were compared using objective criteria and temperature was collected under constant wakeful conditions.