Ventilation causing an average CO₂ concentration of 1,000 ppm has negative impacts on sleep: A field-lab study on healthy youth

Poor bedroom ventilation, leading to poor indoor air quality (IAQ), has been shown to reduce sleep quality. Ventilation causing carbon dioxide (CO₂) concentration of 1,000 ppm is assumed to permit optimal sleep quality. Effects of three ventilation levels, at which the average indoor CO₂ concentrations were 750 ppm, 1,000 ppm and 1,300 ppm, on sleep quality, physiological response and next-day work performance were analysed. After a first night for adaptation, thirty-six young and healthy participants slept alone in simulated bedrooms for two nights at each of the three ventilation levels in balanced order. Sleep quality was recorded by a wrist-worn sleep tracker. Physiological parameters were measured before sleep and after waking. The participants’ ratings of the bedroom environment, the intensity of the health symptoms they experienced, andcognitive performance were obtained using questionnaires and tests.
Compared with ventilation at which the average CO₂ concentration was 750 ppm, sleep quality was significantly reduced at the ventilation causing CO2 concentrations of 1,000 ppm and 1,300 ppm: Sleep efficiency reduced by 1.3 % and 1.8 % and time awake increased by 5.0 min and 7.8 min, respectively. Deep sleep duration decreased at the ventilation causing CO₂ concentration of 1,300 ppm as compared to 750 ppm along with a significant increase in salivary cortisol after waking, which suggests increased stress and sympathetic activity. Therefore, ventilation causing an average CO₂ concentration of 1,000 ppm or above in bedrooms should be avoided. Also, participants with poor sleep quality performed worse on tests of cognitive performance the next day.