How do we create a healthier thermal environment for sleep? A review of sleep thermal comfort and sleep quality

The sleeping thermal environment is crucial for maintaining the circadian rhythm and overall health. This paper systematically reviews the development of sleep thermal comfort research over the past two decades. We aim to review and analyse the impact of the sleeping thermal environment on sleep quality and thermal comfort, and to provide scientific insights for optimizing sleeping environments. First, the research methods for assessing the sleeping thermal environment are categorized into three groups: experimental studies, questionnaire surveys, and simulations. Second, we summarize the impact of the thermal environments on sleep quality and thermal comfort, considering occupants’ subjective experiences, specific influencing factors, and individual differences in thermal sensation. Finally, the development of sleep thermal comfort models is reviewed, and their performance is evaluated using four sets of experimental data. Our findings indicate that relying solely on pre-sleep adjustments is insufficient to fully meet health and comfort needs during sleep. Factors such as indoor air temperature, humidity, airflow, and bed microclimate significantly affect sleep quality and sleep thermal comfort, with particular emphasis on the roles of airflow and bedding microclimate. Additionally, the study highlights differences in thermal requirements and perception between and within individuals. We conclude by identifying key areas for improvement and outlining future research directions to advance the field and enhance the design and control of practical sleep spaces.