Environmental factors affecting sleep quality in summer: a field study in Shanghai, China.

Although the environment can greatly influence an individual's sleep quality, China is yet to conduct comprehensive research on the topic. This study investigated the bedroom environment and sleep quality of 41 households during summer in Shanghai. Bedroom environments were comprehensively evaluated through environmental perception questionnaires filled by participants after waking up every morning. Parameters, such as air temperature, relative humidity, CO2 concentration, and noise level were continuously monitored. Furthermore, participants' sleep quality was observed using both subjective questionnaires and physiological measures. Environmental measurements showed that the most comfortable air temperature and relative humidity was 24.8 °C and 64%, respectively. Physiological measurements showed that the average duration of slow wave sleep (SWS) and sleep efficiency (SE) was 73.8 min and 86.7%, respectively. Additionally, SWS was negatively correlated with air temperature (r = -0.377, p = 0.015) and CO2 concentration (r = -0.362, p = 0.02), and SE was negatively correlated with noise level (r = -0.32, p = 0.042). The subjective and objective results consistently indicated that higher air temperature, CO2 concentration, and noise level leads to poor sleep quality in summer. In addition, air temperature and CO2 concentration had a greater impact on the sleep quality of males, while noise level had a greater impact on the sleep quality of females.