How Bedroom Ventilation Impacts Sleep and Cognitive Function
Opening or closing your bedroom door and window at night can significantly alter air quality, impacting both sleep and cognitive performance the next day. Research from the Technical University of Denmark (DTU) investigated how air quality in bedrooms influences nighttime rest and mental functions upon waking.
The Link Between Air Quality and Sleep
A 2023 doctoral thesis from DTU, titled “Bedroom ventilation and sleep quality,” analyzed data collected in climate chambers and residential rooms in Denmark and Belgium. The research combined laboratory experiments, field studies and controlled interventions to measure the effects of ventilation on objective and subjective indicators of sleep.
The study found that reduced ventilation, indicated by an increase in carbon dioxide (CO₂) concentration from an average of 800 ppm to up to 1,700 ppm, was associated with increased sleep latency (the time it takes to fall asleep) and a reduction in deep sleep. As Pawel Wargocki, an associate professor at DTU Sustain, explains, “The air quality in the bedroom can affect your cognitive abilities, such as your ability to concentrate, understand and react. Sleeping in a well-ventilated room benefits your cognitive abilities.”
CO₂ Levels and Cognitive Performance
Beyond sleep stages, researchers observed that participants reported better cognitive performance after nights with improved ventilation. Objective tests conducted the following morning showed improvements when individuals slept in environments with lower CO₂ concentrations. In one field study, increasing CO₂ from 856 ppm to 1,927 ppm resulted in less deep sleep, more light sleep, and more nighttime awakenings. A similar increase, from 812 ppm to 1,369 ppm, also significantly reduced deep sleep.
Conversely, ventilating rooms with open windows, reducing CO₂ concentration to around 761 ppm, led to increased sleep duration and improved cognitive performance the next day.
Ventilation Recommendations
While CO₂ isn’t necessarily the direct cause of these effects, it serves as a marker for ventilation quality and the presence of bioeffluents (pollutants associated with human respiration). The research measured CO₂ emission rates during sleep – approximately 11 liters per hour per healthy adult – data relevant for designing ventilation systems.
The study recommends a ventilation rate of approximately 10 liters per second per person during sleep. For an average 32 m³ room, this equates to an air exchange rate of about 1.1 changes per hour. Surveys in Denmark revealed a median air exchange rate of 0.4 changes per hour, falling below more rigorous European standards which recommend up to 0.7 changes per hour.
Opening Windows: A Practical Solution, With Considerations
Opening windows can effectively reduce CO₂, volatile organic compounds (VOCs), and particulate matter (PM10) when mechanical ventilation isn’t available. This practice improved perceived air quality and was linked to longer sleep duration.
Though, the authors caution that opening windows requires considering potential drawbacks, such as external noise, urban pollution, and thermal discomfort.
Study Limitations
The thesis acknowledges limitations, including a relatively small number of participants in some experiments and a focus on healthy adults without chronic sleep disorders. The results may not be generalizable to all populations. Nevertheless, the function contributes to the scientific understanding of the impact of nighttime ventilation on health and underscores the importance of air quality during sleep.