The effects of two different kinds of quilt on human core temperature during night sleep

Effects of thermal environment on sleep and circadian rhythm

The thermal environment is one of the most important factors that can affect human sleep. The stereotypical effects of heat or cold exposure are increased wakefulness and decreased rapid eye movement sleep and slow wave sleep. These effects of the thermal environment on sleep stages are strongly linked to thermoregulation, which affects the mechanism regulating sleep. The effects on sleep stages also differ depending on the use of bedding and/or clothing. In semi-nude subjects, sleep stages are more affected by cold exposure than heat exposure. In real-life situations where bedding and clothing are used, heat exposure increases wakefulness and decreases slow wave sleep and rapid eye movement sleep. Humid heat exposure further increases thermal load during sleep and affects sleep stages and thermoregulation. On the other hand, cold exposure does not affect sleep stages, though the use of beddings and clothing during sleep is critical in supporting thermoregulation and sleep in cold exposure. However, cold exposure affects cardiac autonomic response during sleep without affecting sleep stages and subjective sensations. These results indicate that the impact of cold exposure may be greater than that of heat exposure in real-life situations; thus, further studies are warranted that consider the effect of cold exposure on sleep and other physiological parameters.

Effects of two kinds of pillow on thermoregulatory responses during night sleep

We compared thermoregulatory responses during night sleep between two kinds of pillow. One has special cool medium consisting of sodium sulfate and ceramic fiber (pillow A) and the other polyester padding (pillow B). The subjects wore 100% cotton thin pajamas with short sleeves and three-quarters trousers for summer use. They lay and slept in bed with cotton sleeping mat and cotton quilt between 10:30 p.m. and 6:30 a.m. in a bed room with an ambient temperature (Ta) of 27 +/- 1 degrees C and a relative humidity of 55 +/- 5%, using either of the pillow A or pillow B. When they awoke, the subjects filled out a questionnaire on how well they slept during sleep. Main results were: 1) Rectal and forehead skin temperatures and heart rate were kept significantly lower in the pillow A during the latter half of the night sleep. 2) Palm and thigh skin temperatures were significantly higher mostly in the pillow A. 3) All the subjects regarded the pillow A better for deeper sleep. It was concluded that slight cooling of the head due to the pillow A during night sleep seemed to be of significance for deep sleep.