Every year in the U.S., nearly 800,000 individuals suffer a stroke—a serious, sometimes deadly condition caused by a blockage of oxygen or blood flow to the brain. It is considered well-established that unhealthy habits, including poor diet, lack of exercise, and nicotine use can all increase your chances of having a stroke. However, experts now say that there’s one surprising thing you may be doing in the afternoon that appears to be linked with a higher stroke risk—and to most, it’s not considered unhealthy at all. Read on to discover why doing this one thing may be hurting your health, and which other related habits have a similarly dangerous effect.
A 2020 study published in the medical journal Neurology explored possible links between sleep duration, napping, sleep quality, and risk of stroke. By analyzing data from 31,750 participants, the researchers learned that taking a long nap during the day—one that lasts for 90 minutes or more—is associated with a 25 percent higher risk of ischemic stroke when compared with those who nap for 30 minutes or fewer.
However, there is some evidence to suggest that your stroke risk and cardiovascular health may benefit from short naps as needed. A 2019 study published in the journal Heart analyzed the health data of 3,462 residents of Lucerne, Switzerland, and found that those who napped once or twice per week saw their risk of stroke, heart attack, or heart failure reduced by 48 percent compared with those who never napped.
Similarly, those who slept for nine or more hours each night had a 23 percent greater stroke risk than those who slept for seven to eight hours per night. “Persistently long sleep duration or switching from average to long sleep duration increased the risk of stroke,” the team wrote.
Though the researchers found that shorter sleep—characterized as less than six hours of sleep per night—had no observable effect on stroke risk, other studies have observed such an association. “Compared with sleep duration of six to eight hours per day, the risk ratio of stroke was 1.63 (1.23–2.11) times for sleep duration less than six hours per day and 1.40 (1.08–1.75) times for more than eight hours per day,” said a 2020 study published in the journal Scientific Reports. That team noted that women who slept for less than six hours were at higher risk of stroke than men who did the same.
Additionally, the researchers found that having poor overall sleep quality was linked with higher risk of stroke. “Compared with good sleep quality, those with poor sleep quality showed a 29 percent, 28 percent, and 56 percent higher risk of total, ischemic, and hemorrhagic stroke, respectively,” the study says.
Once again, the Scientific Reports findings on sleep quality and stroke risk echoed the Neurology study—they, too, observed heightened risk under these conditions. They added that “men with poor sleep quality had higher stroke risk than women with poor sleep quality.”
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Though the findings may seem to indicate that you would be wise to limit your daytime or nighttime sleep and focus on quality rather than quantity, experts from Harvard Health Publishing have shared crucial insights that may cast the Neurology study’s findings in a new light. They say that while the study found an association between sleep habits and stroke risk, the research did not establish causation. With that in mind, they offered some possible explanations for how sleep and stroke may be linked, besides direct cause.
The Harvard team says that depression, a sedentary lifestyle, or obstructive sleep apnea are all examples of conditions that can lead to the sleep patterns in question, and have also been linked to a higher likelihood of stroke. Since none of these conditions would have their symptoms relieved by intentionally cutting back on precious sleep—and in fact, they could each be exacerbated by less sleep overall—cutting down on your sleep time is not currently recommended. Instead, speak with your doctor if your own sleep patterns seem to be cause for concern.