Air quality, noise among environmental variables linked to decreased sleep efficiency

Key takeaways:

• High noise showed the most robust negative association with sleep efficiency.
• Researchers suggested humidity plays an important role in individuals’ sleep perception.

Air quality, noise and temperature levels were all associated with decreased sleep efficiency, according to a recent study, although such associations may not be apparent to individuals.

The data reflect baseline data from the Green Heart Project (GHP), a prospective greening intervention that “seeks to investigate how planting 8,000 mature trees can improve health through improved pollution and climate,” Mathias Basner, MD, PhD, MSc, a professor in the department of psychiatry at the University of Pennsylvania School of Medicine, told Healio.

“We are specifically interested in sleep and the bedroom environment as a mediator of this,” Basner said.

Previous literature lacks information on bedroom exposures, Basner and colleagues wrote in Sleep Health. In addition, prior studies typically examined just one environmental variable’s link to sleep. Thus, the researchers analyzed multiple variables, including sound levels, carbon dioxide (CO₂), particulate matter 2.5 (PM2.5), temperature, barometric pressure and humidity.

Among the 130 participants recruited from GHP, a subset of 62 participants (mean age, 47 years; 62.9% women) who wore a wrist-actigraph for 24 hours per day for 14 consecutive days were included in an analysis assessing the effects air quality, sound levels and actigraphy. Participants also self-reported assessments of variables and sleep quality through questionnaires.

Basner and colleagues found that:

• high noise was associated with a 4.7% decline in sleep efficiency compared with low noise;
• high CO₂ was associated with a 4% decline in sleep efficiency compared with low CO₂;
• high temperature was associated with a 3.4% decline in sleep efficiency compared with low temperature; and
• high PM_2.5 was associated with a 3.2% decline in sleep efficiency compared with low PM_2.5.

“I wasn’t expecting a ‘hit’ on four out of the six measured variables,” Basner said. “It was nice to see confirmed that we have very little insight to what happens [to] us during sleep, as most variables were only reflected in objective sleep outcomes.”

Though barometric pressure and humidity showed no associations with sleep efficiency, the researchers wrote that bedroom humidity was the only variable associated with any sleep outcomes in questionnaires, which suggests that “humidity plays an important role in sleep perception.”

Furthermore, most patients self-reported that levels of temperature and humidity were just right, and they were not at all disturbed by the level of noise despite actual exposure levels.

“Humans are unconscious and unaware of themselves and their surroundings during the sleep period for most of the night, which is why subjective assessments have to rely on typically short periods of intermittent wakefulness,” Basner and colleagues wrote. “Also, self-report ratings like sleepiness have been shown to habituate quickly, especially in chronic exposure situations.”

Compared with other associated environmental variables, “the negative associations of noise with [sleep efficiency] were the most robust,” the researchers wrote.

Thus, “the importance of the bedroom environment for sound sleep needs to be stressed more,” Basner said.

The researchers highlighted several potential interventions for improving sleep efficiency, which include behavioral changes — such as leaving hallway doors open to reduce carbon dioxide — and changes to building structures, like three-pane windows to lower noise levels.

Moving forward, “we are still waiting for funding for the follow-up measurements post-greening,” Basner said.

“Also, taking this to other geographic regions and populations would be a natural next step,” he said.

References:

• Basner M, et al. Sleep Health. 2023;doi:10.1016/j.sleh.2023.02.010.
• Penn Medicine study links air pollution, heat, carbon dioxide, and noise to reduced sleep. https://www.pennmedicine.org/news/news-releases/2023/april/sleep-efficiency. Published April 18, 2023. Accessed April 21, 2023.