Influence on human sleep patterns of lowering and delaying the minimum core body temperature by slow changes in the thermal environment.

Study Objectives: We hypothesized that appropriate changes in thermal environment would enhance the quality of sleep.

Design/setting: Controlled laboratory study.

Participants: Healthy young men (n = 7, mean age 26 years).

Interventions: Nocturnal sleep structures in semi-nude subjects were compared between a condition where an ambient temperature (Ta) of 29.5 degree C was maintained throughout the night (constant Ta), and a second condition (dynamic Ta) where Ta changed slowly within the thermoneutral range (from 27.5 C to 29.5 degree C).

Measurements And Results: Statistically significant (P < 0.05) results included a lower and a later occurrence of minimum core body temperature (Tc), and a longer duration of slow-wave (stages 3+4) sleep in dynamic versus constant T. However, total sleep time, sleep efficiency, the total durations of light (stages 1+2) and rapid eye movement sleep, and the latencies to sleep onset, slow-wave sleep, and rapid eye movement sleep did not differ between conditions.

Conclusions: Lowering the minimum and delaying the nadir of nocturnal Tc increases slow-wave sleep (probably by an increase of dry heat loss); use of this tactic might improve the overall quality of sleep.