Opening windows and doors before going to bed can reduce carbon dioxide levels in bedrooms and improve sleep quality, according to new research from the Eindhoven University of Technology, the Netherlands.

Dr. Asit Kumar Mishra, a postdoctoral researcher in the Department of the Built Environment, Unit Building Physics and Services at the Eindhoven University of Technology, and colleagues examined window and door opening as means of bedroom ventilation and the consequent effect upon occupants’ sleep, using data from 17 healthy volunteers.

“A mixed-methods approach was used to study the sleeping environment under two different conditions of ventilation,” Dr. Mishra and co-authors explained.

“One condition was with an open window or door (‘open’) and the other with closed windows and door (‘closed’).”

The researchers measured carbon dioxide levels, temperature, background noise, and relative humidity in the bedrooms.

Qualitative assessment of sleep was done using sleep questionnaires, while quantitative assessment was done through actigraphy and sleep monitoring (using a Sensewear Armband) and movement detection (using a FlexSensor).

“Average carbon dioxide level for the ‘open’ conditions was 717 ppm (particles per million) and for ‘closed’ conditions was 1150 ppm,” the scientists said.

“Absolute humidity levels were similar for both conditions, while ‘open’ conditions were slightly cooler (mean temperature was 19.7 degrees Celsius) than ‘closed’ (20.1 degrees Celsius).”

“Participants subjective assessment of their sleep depth correlated with carbon dioxide levels,” they said.

“Objectively measured sleep efficiency and number of awakenings, which were assessed through senses worn during sleep, also correlated with carbon dioxide levels.”

“Lower carbon dioxide levels implied better sleep depth, sleep efficiency, and lesser number of awakenings.”

The findings are published in the journal Indoor Air.

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A.K. Mishra et al. Window/door opening-mediated bedroom ventilation and its impact on sleep quality of healthy, young adults. Indoor Air, published online November 21, 2017; doi: 10.1111/ina.12435