2022 Volume 25 Issue 1 Pages 31-42
We conducted a summertime field survey of the bedroom thermal environments and nocturnal sleep of elderly people living in urban and rural areas of Nara Prefecture in Japan. This study aimed to evaluate bedroom thermal environments and examine the effects on sleep quality. The field survey was conducted for one week from July 2017 to September 2019. A total of 86 elderly people were surveyed (51 in the target urban area and 35 in the target rural area; mean age 74.8 ± 10.3 years). The air temperature and relative humidity in participants’ bedrooms were measured to monitor the thermal environment during participants’ nocturnal sleep. Participants’ body movement during sleep was measured using an activity meter worn around their waists, and sleep parameters such as time in bed and sleep efficiency were calculated. Participants rated their sleep quality using a subjective sleep evaluation (OSA sleep inventory MA version), thermal sensation, and thermal comfort after waking up. In addition, participants answered questionnaires on their housing and the use of cooling devices in their bedrooms. Over 60% of participants in the urban area often used air conditioners; in the rural area, they used electric fans and opened windows for ventilation rather than air conditioners to keep cool. Outdoor and bedroom temperatures during the night were higher in the urban than in the rural area. The rate of air conditioner use increased as the outside nighttime temperature increased, suggesting that differences in outdoor temperature influence regional differences in air conditioner use. Most air conditioner users applied timers or turned the system on and off at night, with less than 10% keeping the air conditioner on throughout the night. The mean bedroom temperature during sleep was 28.0°C ± 1.2°C in the urban area and 25.6°C ± 1.4°C in the rural area. We compared the recorded bedroom temperatures to the recommended standard summer bedroom temperature for elderly people (temperature: 23-27°C, relative humidity: 60-80%) and found that 19% of the urban and 68% of the rural area were within standard ranges. Most participants in both urban and rural areas rated their bedroom thermal environments as neutral to cool and comfortable. As bedroom temperatures increased, the wake after sleep onset tended to increase. In addition, the time in bed increased as the wake after sleep onset increased, suggesting that the increase in time in bed prevented the decrease in sleep efficiency. These show that a high-temperature environment affects sleep quality in elderly people. Therefore, it is essential to use air conditioners and adjust bedroom thermal environments appropriately to maintain sleep quality during summer.
