Now might be the time to get blackout curtains and turn off your phone before bed. While being exposed to light at night may seem innocent, it can be harmful to your health.
Exposure to artificial light at night is linked to higher rates of cardiovascular disease, according to recent research published in the journal JAMA Network Open. Specifically, experts noted an increased risk of heart failure, coronary artery disease, atrial fibrillation, myocardial infarction (commonly known as heart attack) and stroke.
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Researchers tracked nighttime exposure for one week among 88,905 adults over the age of 40 who wore wrist sensors to measure their exposure between 12:30 a.m. and 6 a.m.
Participants were divided into four percentiles from the least exposure to nighttime light to the most. The researchers then reviewed their heart health data over 9.5 years and adjusted for established cardiovascular risk factors such as smoking, physical activity, shift work and socioeconomic status.
Compared to those who experienced the least amount of light at night, people with the least amount of light had the worst health outcomes. Those exposed to a lot of light at night were 56% more likely to develop heart failure, up to 56% more likely to have a heart attack, and up to 30% more likely to have a stroke.
There is one main reason why experts believe this happens.
The researchers conclude that the negative health effects of nighttime light are related to the circadian rhythm, which is our body’s 24-hour sleep-wake cycle.
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“We know that the circadian rhythm … is actually an important part of a healthy lifestyle, and that disruptions in this … sleep-wake style cycle can be linked to cardiovascular events,” said UChicago Medicine cardiologist Dr. Jeremy Slivnick.
Exposure to light at night can trick the brain into thinking it’s daytime, which disrupts normal circadian rhythm patterns, Slivnick explained.
“I think exposure to light causes a disruption of circadian rhythms that may or may not affect sleep duration, but definitely affects overall sleep status, which is a combination of not only regular sleep duration but also good sleep,” said Dr. Ehimen Aneni, an assistant professor of cardiovascular medicine at Yale School of Medicine in Connecticut. Aneni is also not involved in the investigation.
Even if you get seven or eight hours of sleep every night, that doesn’t mean you’re getting quality sleep. If you wake up tired or have a headache, you may have a sleep problem that is worth talking to your doctor about.
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Poor sleep is linked to “various cardiovascular and cardiometabolic conditions,” Aneni said. “For example, there is evidence that short sleep duration is associated with an increased risk of heart attacks and strokes, and that sleep disturbances are associated with heart disease and stroke.
Sleep is also our body’s “recharge mechanism,” Slivnick said. “Decreased sleep can increase stress, anxiety, and increase the body’s fight-or-flight mechanisms, and these mechanisms can put stress on the heart, especially over long periods of time, which can increase the risk of cardiovascular disease.”
Chronic stress can lead to problems like high blood pressure, which puts people at greater risk of cardiovascular disease. In addition, circadian rhythm disturbances are a risk factor for developing type 2 diabetes, the study authors wrote. Having diabetes increases the risk of cardiovascular disease.
“Another thing that stuck out to me was that the association seemed to be stronger in women than in men,” Aneni said. The study authors wrote that this finding is consistent with other studies that have found that women are more susceptible to light-induced circadian rhythm disturbances and that women who work night shifts have a higher incidence of heart failure than men.
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There are limitations to the study. First, researchers don’t know the exact light source people were exposed to at night, so it’s not known whether they were affected by street lights, TV screens, tablets, phones, or something else. There was also not much diversity in the group; 97% of participants were Caucasian.
“I hope there will be more studies like this that support these findings and can directly explain why nighttime light causes heart disease — and I’m betting the answers will have to do with the quality and quantity of sleep,” Aneni said.
New research shows that light at night puts people at higher risk of cardiovascular diseases such as heart failure. sestovic via Getty Images
Practice good sleep hygiene, including eliminating light at night, for quality sleep.
Although more research is needed to determine exactly how nighttime light is related to cardiovascular health, limiting exposure is a good way to reduce the risk of heart disease.
“We have a population that actually doesn’t sleep as well as they should and doesn’t value sleep as much,” Aneni said.
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Adults should get seven to nine hours of sleep and go to bed and get up around the same time each day.
“The healthier you sleep, the healthier you are,” added Aneni. “And when it comes to cardiovascular disease, the better your sleep, the lower your risk of cardiovascular disease.”
In addition to turning off the lights while you sleep, limiting bright light from screens before bed, and prioritizing rest, there are other things you can do to improve heart health.
Slivnick said he often refers patients to the American Heart Association’s Life Essential 8, which are eight recommendations to follow for optimal cardiovascular health. These guidelines include:
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Eat nutritious diets that are rich in vegetables, lean proteins, fruits, nuts and seeds.
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Get at least 120 minutes of moderate-intensity exercise (such as walking or gardening) or 75 minutes of vigorous-intensity exercise (such as running or swimming) each week.
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Sleeps seven to nine hours every night.
“If we do those eight things, we can really play a huge role in controlling our risk of cardiovascular disease,” Slivnick said.
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