- People in the top quarter of NO2 exposure (a type of traffic-related air pollution) were 60 percent more likely to have low sleep efficiency over a five-year period
- Among people exposed to the highest levels of fine-particle pollution, there was a 50 percent increased likelihood of low sleep efficiency
- High air pollution levels may also lead to acute sleep effects after short-term exposures, but more research is needed to confirm this
If you’re among the 35 percent of U.S. adults who are not getting the recommended seven hours of sleep each night,1 a silent intruder in your bedroom could be to blame: air pollution. With well-known adverse effects on your heart and lung health, research presented at the American Thoracic Society (ATS) 2017 International Conference suggests poor air quality may also disrupt your sleep.2
The study looked closely at the effects of two widespread pollutants, nitrogen dioxide (NO2), which is traffic-related air pollution, and PM2.5, or fine-particle pollution, which is less than 2.5 micrometers in size and is responsible for reduced visibility. Both of the pollutants had an influence on study participants’ sleep efficiency, which is a measure of the time spent actually sleeping as opposed to lying in bed awake.
In fact, the people in the top quarter of NO2 exposure were 60 percent more likely to have low sleep efficiency over a five-year period compared to those in the lowest quarter. Among those exposed to the highest levels of fine-particle pollution, there was a 50 percent increased likelihood of low sleep efficiency.
The researchers suggested high air pollution levels may also lead to acute sleep effects after short-term exposures, but they did not have adequate data to study the potential connection. Lead study author Dr. Martha E. Billings, assistant professor of medicine at the University of Washington, said in a press release:3
“We thought an effect was likely given that air pollution causes upper airway irritation, swelling and congestion, and may also affect the central nervous system and brain areas that control breathing patterns and sleep … These new findings indicate the possibility that commonly experienced levels of air pollution not only affect heart and lung disease, but also sleep quality. Improving air quality may be one way to enhance sleep health and perhaps reduce health disparities.”
Is Poor Air Quality Interfering With Your Sleep?
Past research has also linked air pollution with poor sleep, adding credence that environmental factors may significantly influence the quality of your shut-eye. In 2015, for instance, researchers investigated the link between black carbon, a marker of traffic-related air pollution, and sleep among participants of the Boston Area Community Health Survey.4 They found that long-term exposure to black carbon may be associated with shorter sleep duration, especially in men.
Among children, meanwhile, exposure to particulate matter with an aerodynamic diameter of less than 10 μm (PM10) was associated with sleep disturbances,5 as was exposure to another form of air pollution — secondhand smoke. In the latter case, children with asthma who were regularly exposed to tobacco smoke at home were more likely to suffer from sleep problems, including longer delays in falling asleep, sleep-disordered breathing, daytime sleepiness and overall sleep disturbance.6
One Bad Night’s Sleep May Slow Your Metabolism
It’s well-known that interrupted or impaired sleep may contribute to a pre-diabetic, insulin-resistant state, making you feel hungry even if you’ve already eaten, which can lead to weight gain. What’s less known is that you don’t have to be a chronic insomniac for the lack of sleep to affect your waistline. In research outlined at the 2017 European Congress of Endocrinology in Lisbon, it was found that disrupted sleep patterns, even for one night, may increase your appetite and slow your metabolism.7
The researchers, from Uppsala University in Sweden, conducted one intriguing experiment that included 14 participants who got varying amounts of sleep, ranging from none at all to normal amounts. Their eating habits, blood sugar, hormone levels and metabolic rate were monitored, revealing that even one night of poor sleep slowed metabolism, including rates of breathing and digestion, by up to 20 percent.
Further, after poor sleep, blood sugar levels rose as did levels of stress hormones and ghrelin, the “hunger hormone” that might work in your brain to make you keep eating “pleasurable” foods when you’re already full. Other experiments by the research team found sleep disturbance reduced insulin sensitivity and altered gut bacteria, the latter of which is also important for healthy metabolism. In short, skimping on sleep sets up the perfect storm for metabolic disturbance and weight gain. As The Guardian reported:8
“[The researchers] found healthy but sleep-deprived people prefer larger food portions, seek more calories, exhibit signs of increased food-related impulsivity, experience more pleasure from food, and expend less energy than control groups. Part of the problem stems from the fact that sleep loss shifts the hormonal balance from those that promote fullness (satiety), such as GLP-1, to those that promote hunger, such as ghrelin. As a result, people think they are hungrier than they really are.”
Lack of Sleep Could Affect Your Social Life
If you’re sleeping in an air-polluted space that’s keeping you up at night (or otherwise have difficulty sleeping), even your social life could suffer. In a study published in the journal Open Science, 25 people were photographed after normal sleep and two days of sleep restriction.9 The photos were then rated by 122 people, based on how much they would like to socialize with that person, attractiveness, health and other factors.
The raters were less likely to want to socialize with people who were sleep-deprived and also perceived them to be less attractive, less healthy and more sleepy. The findings suggest that not only can others likely see it on your face if you’re sleep deprived, but they may be less inclined, by 20 percent to 30 percent, to want to socialize with you as a result.10
If You Have Metabolic Syndrome, Lack of Sleep Increases Risk of Early Death
If you’re struggling with a chronic disease, poor sleep may make it harder to control and increase your risk of serious complications — even premature death. Among people with metabolic syndrome, for instance, those who got more than six hours of sleep per night were 1.5 times more likely to die of stroke during the 16-year study period compared to 2.1 times as likely for those who slept for under six hours.11
Among people with metabolic syndrome who slept for six hours or less, the risk of death from any cause was also nearly twice as high as it was among people without the condition. “Short sleep in individuals with MetS [metabolic syndrome] may be linked to greater central autonomic and metabolic dysfunction,” the researchers added, suggesting that future trials should look at whether getting more sleep improves outcomes in people with the disease.12
The latter appears to be likely. In 2014, poor sleep was once again found to have a significant bearing on metabolic disorders such as obesity, hypertension and type 2 diabetes, and the researchers suggested addressing your sleeping habits may be key for both the prevention and treatment of these disorders.13
Losing Sleep Takes a Toll on Your Heart
Your whole body suffers when you don’t get enough sleep. Some of the repercussions you can feel (via daytime fatigue, for instance) but many, like the adverse effects on your heart, you cannot. Researchers from the University of Bonn in Germany took images of radiologists’ hearts before and after a 24-hour shift, during which they got only about three hours of sleep. Significant heart strain, a precursor to heart problems, was noted following the sleep deprivation.14
Other concerning changes, including an increase in blood pressure, heart rate and thyroid hormones, which is indicative of a stress response, were also noted. Getting back to air pollution, if you’re sleep deprived and exposed to air pollution, it’s a double whammy to your heart health, as even sporadic exposure to PM2.5 was associated with an increase in endothelial cell death and elevations of specific immune cells that could contribute to the development of atherosclerosis and acute coronary events.15
How to Improve the Air Quality in Your Bedroom
The featured study looked at the role of outdoor air pollution and sleep, but there’s good reason to believe that in creating your bedroom sleep sanctuary, attention to proper indoor air quality should also be given (plus, while you can’t control the air quality outside of your home, you can control, to some extent, the quality of the air inside it). Filtering your home’s air is a good start.
Commercially purchased air filters may change measurements of health, include lowering the amount of C-reactive protein and other measurements of inflammation and blood vessel function.16 Not all filters work with the same efficiency to remove pollutants from your home, and no one filter can remove all pollutants, so be sure to do your research on the different types of air filters to meet your specific needs. Another option is to add houseplants, which help to absorb indoor air pollution.
Further, one of the simplest and easiest ways to reduce the pollution count in your home is to open the windows and let a little fresh air in (assuming the outdoor air isn’t overly polluted). Because most homes have little air leakage, opening the windows for as little as 15 minutes every day can improve the quality of the air you’re breathing. You may also want to consider cracking the window at night while you sleep. Installing an attic fan is another way of bringing fresh air into your home and reducing your air conditioning costs.
The Basics of Good Sleep
Air quality is just one of many factors that influence the quality of your sleep. Perhaps the most important natural “trick” of all for improving your sleep is to make sure you’re getting proper exposure to bright light during the day and no exposure to blue light at night. In the morning, bright, blue light-rich sunlight signals to your body that it’s time to wake up. At night, as the sun sets, darkness should signal to your body that it’s time to sleep.
Ideally, to help your circadian system reset itself, get at least 10 to 15 minutes of natural light first thing in the morning. This will send a strong message to your internal clock that day has arrived, making it less likely to be confused by weaker light signals later on. Then, around solar noon, get another “dose” of at least 30 minutes’ worth of sunlight.
A full hour or more would be even better. If your schedule is such that you have to get up and arrive at work before sunrise, aim to get at least that half-hour of bright sunlight sometime during the day.
In the evening when the sun begins to set, put on amber-colored glasses that block blue light. You can also dim your lights (whether they’re LED, incandescent or compact fluorescent lamps [CFLs]) and turn off electronic devices to reduce your exposure to light that may stifle your melatonin production. Better still, swap out LEDs for incandescent or low-voltage incandescent halogen lights (and please be sure to read my article on the dangers of LED lights).
After sundown, you can also shift to a low-wattage bulb with yellow, orange or red light if you need illumination. A salt lamp illuminated by a 5-watt bulb is an ideal solution that will not interfere with your melatonin production. Candle light also works well. If you’ve already optimized your light exposure and air quality and are still struggling with sleep, see my 33 healthy sleep secrets for a more comprehensive list of strategies for a better night’s rest.