Air pollution, heat, and high levels of carbon dioxide and ambient noise may all adversely affect our ability to get a good night's sleep, according to a study.
The research, published in the journal Sleep Health, is one of the first to measure multiple environmental variables in the bedroom and analyse their associations with sleep efficiency—the time spent sleeping relative to the time available for sleep.
The researchers found that in a group of 62 participants tracked for two weeks with activity monitors and sleep logs, higher bedroom levels of air pollution (particulate matter less than 2.5 micrometres in size, or PM2.5), carbon dioxide, noise, and temperature were all linked independently to lower sleep efficiency.
"These findings highlight the importance of the bedroom environment for high-quality sleep," said study lead author Mathias Basner, a professor at the University of Pennsylvania, U.S.
In addition to work and family obligations that compete with sleep for time, a quickly changing environment due to growing urbanisation and climate change seems to have made it harder to get a good night's sleep, the researchers said.
Sleep that is of inadequate duration or efficiency due to frequent disruptions affects work productivity and quality of life. It also has been linked to a higher risk of chronic diseases, including heart disease, type 2 diabetes, depression, and dementia, they said.
The team, including researchers from the University of Louisville, US, recruited participants from the National Institutes of Health Green Heart Project, which investigates the effects of planting 8,000 mature trees on the cardiovascular health of Louisville residents.
For each of the environmental variables measured, the researchers compared sleep efficiency during exposures to the highest 20% of levels versus the lowest 20% of levels.
They found that high noise was associated with a 4.7% decline in sleep efficiency, high carbon dioxide with a 4% reduction, high temperature with a 3.4% decline, and high PM2.5 with a 3.2% reduction.
Two other sleep environment variables, relative humidity and barometric pressure, appeared to have no significant association with sleep efficiency among the participants, according to the researchers.
"We seem to habituate subjectively to our bedroom environment and feel there is no need to improve it, when in fact our sleep may be disturbed night after night, as evidenced by the objective measures of sleep we used in our study," Basner added.
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