Associations of bedroom temperature and ventilation with sleep quality

Abstract

Sleep is essential for the body to recover from both physical and psychological fatigue accruing throughout the day, and to restore energy to maintain bodily functions. Bedroom environmental quality is one of the key causes of sleep disturbance, so a better understanding of the associations of bedroom temperature and ventilation rate (using CO2 as the surrogate) with sleep quality is necessary. This field study was conducted during summer in subtropical Sydney, Australia, with a sample of 48 householders, including both males and females. In addition to a questionnaire-based subjective sleep quality scales, sleep metrics were also monitored using wrist-wearable sensors. An indoor environmental quality monitoring station (SAMBA) was installed in each survey bedroom for continuous measurements of thermal and air quality parameters at 5-minute intervals for five consecutive days for each subject. The thermal sensation subjects used to characterize their night’s sleep showed no relationship with the actual thermal conditions prevailing in the bedroom while sleeping. Sleep efficiency (ratio of time asleep to time in bed) and rapid eye movement (REM) sleep (%) were both negatively correlated with bedroom operative temperature; as bedroom operative temperature increases by 1 K, the estimate of sleep efficiency and REM sleep percentage decrease by 1.036% and 1.647%, respectively. Deep sleep percentage was negatively related to bedroom CO2 concentration, with a 4.3% decrement for every 100 ppm increase in the overnight mean CO2 concentration. The deterioration in subjectively evaluated air freshness was associated with poorer self-reported sleep quality. The effect of bedroom CO2 concentration on light sleep percentage varied significantly under different bedroom operative temperature levels.