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

Exercise Sciences Research Group, Tokyo Metropolitan Institute of Gerontology, Itabashi, Tokyo, Japan.
Sleep (Impact Factor: 4.59). 07/2007; 30(6):797-802.
Source: PubMed


We hypothesized that appropriate changes in thermal environment would enhance the quality of sleep.
Controlled laboratory study.
Healthy young men (n = 7, mean age 26 years).
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).
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.
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.

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Available from: Takayuki Ishiwata, Oct 05, 2015
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    • "They demonstrated a SkBF circadian variation that was out of phase with the T re circadian variation by 4 h; decreases in T re were preceded by increases in extremity SkBF. These physiological responses develop sleep architecture and ensure a continuous decrease in T c during nocturnal sleep although T c was to some extent influenced by varying ambient temperature as demonstrated by Dewasmes et al. (1994, 1996), Togo et al. (2007) and Wakamura and Tokura (2002). As opposed to aforementioned circadian regulation before and during nocturnal sleep, not much circadian effect may be expected to maintain the diurnal rhythm of T c during the daytime, particularly in the afternoon. "
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    ABSTRACT: In this study, the hypothesis is tested that continuous increases in ambient temperature (Ta) during daytime would give elevated core and skin temperatures, and consequently better thermal sensation and comfort. Rectal temperature (Tre), skin temperatures and regional dry heat losses at 7 sites were continuously measured for 10 Japanese male subjects in three thermal conditions: cond. 1, stepwise increases in Ta from 26 °C at 9 h00 to 30 °C at 18 h00; cond. 2, steady Ta at 28 °C from 9 h00 to 18 h00 and cond. 3, stepwise decreases in Ta from 30 °C at 9 h00 to 26 °C at 18 h00. Oxygen consumption was measured and thermal sensation and comfort votes were monitored at 15 min intervals. Body weight loss was measured at 1 h intervals. While Tre increased continuously in the morning period in any condition, it increased to a significantly greater (p < 0.05) 36.9 ± 0.3 °C at 18 h00 in cond. 1 relative to 36.7 ± 0.28 °C in Cond. 2 and 36.5 ± 0.37 °C in cond. 3. Better thermal comfort was observed in the afternoon and the evening in Cond.1 as compared with the other 2 conditions. Thus, a progressive and appropriate increase in Ta may induce optimal cycle in core temperature during daytime, particularly for a resting person.
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