Experimental study of the negative effects of raised bedroom temperature and reduced ventilation on the sleep quality of elderly subjects

This study investigated the effects of air temperature and ventilation on the sleep quality of elderly subjects and elucidated the mechanisms involved. Sixteen subjects aged over 65 years old were exposed to four conditions in a 2 x 2 design: air temperatures of 27 degrees C and 30 degrees C (with a ceiling fan in operation at 30 degrees C) and two ventilation conditions (with and without mechanical ventilation) in experimental bedrooms. Their electroencephalogram, electrooculogram, chin electromyogram, electrocardiogram, respiration, oxygen saturation, and wrist skin temperature were measured continuously during sleep. Saliva samples were collected, and blood pressure was measured both before and after sleep. The results showed that at the temperature of 30 degrees C, the total sleep time, sleep efficiency, and duration of REM sleep of the elderly decreased by 26.3 min, 5.5%, and 5.3 min, respectively, and time awake increased by 27.0 min, in comparison with 27 degrees C, indicating that the sleep quality of the elderly is very vulnerable to heat exposure. Even a small heat load led to an overactive sympathetic nervous system and increased wrist skin temperature, which reduced sleep quality. Improving the ventilation increased the duration of deep sleep and REM sleep by 10.3 min and 3.7 min, respectively. Higher pollutant concentrations affected the respiration and autonomous nervous systems to reduce sleep quality. The benefits of improved thermal environment and ventilation on sleep quality were found to be additive. Good ventilation and the avoidance of raised temperatures in the bedroom are thus both important for the sleep quality of the elderly.