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Poor sleep habits directly linked to environmental pollutants

A recent study led by researchers at the Perelman School of Medicine at the University of Pennsylvania has revealed that air pollution, high levels of carbon dioxide, ambient noise, and warm temperatures may all have negative impacts on our ability to get a good night’s sleep. 

The study, published in the journal Sleep Health, is among the first to examine multiple environmental variables in the bedroom and their associations with sleep efficiency, which is the time spent sleeping relative to the time available for sleep.

Over a period of two weeks, 62 participants were monitored using activity trackers and sleep logs. The experts found that higher bedroom levels of air pollution (particulate matter <2.5 micrometers or PM2.5), carbon dioxide, noise, and temperature were all independently linked to lower sleep efficiency. 

“These findings highlight the importance of the bedroom environment for high-quality sleep,” said study lead author Dr. Mathias Basner, director of the division of Sleep and Chronobiology in the Department of Psychiatry at Penn Medicine.

Problems associated with poor sleep

Inadequate sleep duration and efficiency due to frequent disruptions, such as “tossing and turning,” can affect work productivity and quality of life, as well as being linked to a higher risk of chronic diseases like heart disease, type 2 diabetes, depression, and dementia. 

As urbanization and climate change continue to rapidly alter our environment, the ability to achieve a good night’s sleep is becoming increasingly difficult.

The study, which was conducted in collaboration with the Christina Lee Brown of the University of Louisville, is among a limited number of studies that have looked at associations between multiple objectively measured factors in the sleep environment and objectively measured sleep. 

Participants were recruited from the National Institutes of Health-funded Green Heart Project, which investigates the effects of planting 8,000 mature trees on the cardiovascular health of Louisville residents.

Results of the study

Comparing sleep efficiency during exposures to the highest 20 percent of environmental variable levels versus the lowest 20 percent, the researchers measured the following:  

  1. High noise was associated with a 4.7 percent decline in sleep efficiency compared to low noise. 
  2. High carbon dioxide was associated with a 4.0 percent decline compared to low levels.
  3. High temperature was associated with a 3.4 percent decline compared to low temperature. 
  4. High PM2.5 was associated with a 3.2 percent decline compared to low PM2.5. 

Two other sleep environment variables, relative humidity and barometric pressure, appeared to have no significant association with sleep efficiency among the participants.

Interestingly, only bedroom humidity was associated with sleep outcomes assessed through questionnaires, with higher humidity being linked to lower self-reported sleep quality and more daytime sleepiness. 

This indicates that studies based on questionnaires might miss significant associations that can be detected by objective measures of sleep. As humans are unconscious and unaware of their surroundings during large portions of their sleep period, this is not surprising.

Moreover, most study participants rated humidity, temperature, and noise levels in the bedroom as “just right,” regardless of the actual exposure levels. 


“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,” said Dr. Basner.

The researchers recommend further investigation into interventions that could improve sleep efficiency by reducing exposure to these sleep-disrupting factors. 

“This could be as simple as leaving a bedroom door open to lower carbon dioxide levels, and using triple-pane windows to reduce noise,” said Dr. Aruni Bhatnagar. “We also applied for funding that will allow us to investigate whether planting trees can improve sleep and cardiovascular health through improving health behaviors and the bedroom environment.”

More about sleep disorders

Sleep disorders are conditions that prevent individuals from achieving sufficient restorative sleep, which can lead to negative effects on their physical, mental, and emotional well-being. Some common sleep disorders include insomnia, sleep apnea, restless legs syndrome (RLS), narcolepsy, and circadian rhythm sleep-wake disorders. Several factors can contribute to poor sleep, including:

Lifestyle and habits

Irregular sleep schedules, excessive consumption of caffeine or alcohol, smoking, and engaging in stimulating activities close to bedtime can disrupt sleep patterns.

Stress and anxiety

High levels of stress and anxiety can interfere with falling asleep and staying asleep, leading to poor sleep quality.

Medical conditions

Sleep disorders can be caused or exacerbated by underlying medical conditions, such as sleep apnea, chronic pain, or neurological disorders.

Mental health disorders

Conditions like depression, anxiety, and bipolar disorder can contribute to sleep disturbances, creating a bidirectional relationship between sleep and mental health.

Environmental factors

As mentioned in the previous response, factors such as air pollution, high levels of carbon dioxide, ambient noise, and warm temperatures can all negatively impact sleep quality.


Certain medications can interfere with sleep, including antidepressants, stimulants, and medications for high blood pressure or asthma.


Sleep patterns change as we age, and older adults may experience more difficulty falling asleep and staying asleep.


Genetic factors can influence an individual’s susceptibility to sleep disorders, such as narcolepsy or RLS.

Poor sleep hygiene

Inadequate sleep habits, such as irregular bedtimes, excessive screen time before bed, and an uncomfortable sleep environment, can lead to poor sleep quality.

Circadian rhythm disruptions

Shift work, jet lag, or exposure to excessive artificial light at night can interfere with the body’s natural sleep-wake cycle, leading to sleep disturbances.

To improve sleep quality, individuals can practice good sleep hygiene, maintain a consistent sleep schedule, create a comfortable sleep environment, manage stress and anxiety, treat underlying medical conditions, and consult with a healthcare professional if sleep problems persist.


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