A recent Indoor Air study found that opening windows or doors before going to bed can reduce carbon dioxide levels in bedrooms and improve sleep quality.
Participants subjective assessment of their sleep depth, which was obtained through questionnaires, correlated with carbon dioxide levels. 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.
Bedsharing may impair sleep quality
A. K. Mishra et al, Window/door opening-mediated bedroom ventilation and its impact on sleep quality of healthy, young adults, Indoor Air (2017). DOI: 10.1111/ina.12435