Reduced sleep efficiency is related to air quality, temperature levels, and noise, according to study findings published in Sleep Health: Journal of the National Sleep Foundation.
The bedroom environment plays a key role in sleep quality. Most recommendations specific to the bedroom focus on air quality, darkness, noise, temperature, and humidity. However, most studies about how the bedroom environment affects sleep quality only focus on a few bedroom characteristics.
For the study, researchers recruited participants from the Green Heart Project (GHP; ClinicalTrials.gov Identifier: NCT03670524), which focused on cardiovascular effects of planting mature trees in Louisville, Kentucky. A subset of participants (N=62) underwent 14 days of 24-hour actigraph surveillance and continuous measuring of particulate matter, temperature, humidity, carbon dioxide (CO2), barometric pressure, and noise in their bedroom.
The participants were mean age, 47.7 (SD, 13.2) years; 62.9% were women; and, they had a body mass index (BMI) of 30.5 (SD, 6.4) kg/m2.
In the bedroom, these were the averages for the following characteristics:
- Particulate matter 2.5 (PM2.5): 10.6 (SD, 47.0) mg/m3
- Relative humidity: 51.2% (SD, 7.3%)
- Temperature: 73.3°F (SD, 4.3°F)
- Carbon dioxide (CO2): 1194.0 (SD, 523.5) parts per million (ppm)
- Barometric pressure: 999.8 (SD, 2.7) hectopascal (hPa)
- Sound pressure: 49.3 (SD, 7.8) decibels A (dBA)
During the sleep period, PM2.5 and sound decreased while humidity and CO2 increased.
The only environmental variables that correlated with each other were humidity and PM2.5, both within (r, 0.37) and across (r, 0.40) nights.
The participants averaged 6.23 (SD, 1.43) hours of sleep on weekdays and 6.51 (SD, 1.47) hours on weekends; and, sleep efficiency averaged 82.4% (SD, 8.0%) and 82.8% (SD, 7.0%) on weekdays and weekends, respectively.
Bed sharing occurred on 62.2% of nights. The participants also napped on 16.9% and exercised on 43.0% on weekdays; they also reported caffeine and alcohol consumption in the 6 hours before bed in 28.2% and 19.0% of weekdays, respectively.
On a 5-point Likert scale where 5 was the worst, participants rated their stress as 2.1, sleep quality as 2.4, tiredness as 2.8, and noise disturbance as 1.4.
In the fully adjusted model, sleep efficacy associated with PM2.5 (P <.05), temperature (P <.05), CO2 (P <.05), and noise (P <.0001). After z-transformation, sleep efficacy was related with PM2.5 (b, -2.15%; P <.0001), temperature (b, -1.73%; P <.0001), and noise (b, -1.85%; P <.0001).
In addition, the covariates of elapsed sleep time and prebed alcohol consumption significantly affected sleep efficacy.
This study may have been limited by not assessing light levels or volatile compounds.
The researchers concluded, “These findings add to a growing body of evidence highlighting the importance of the bedroom environment — beyond the mattress — for high-quality sleep.”
Basner M, Smith MG, Jones CW, et al. Associations of bedroom PM2.5, CO2, temperature, humidity, and noise with sleep: an observational actigraphy study. Sleep Health. Published online April 18, 2023. doi:10.1016/j.sleh.2023.02.010