Stroke risk linked to both too little and too much sleep

• Researchers investigated the link between sleep problems and stroke risk.
• They found that sleep problems increased stroke incidence by as much as five times.
• Further studies are needed to confirm the results.

Quality sleep is essential for health. Sleep problems range from too short or too long sleep duration, difficulty falling and staying asleep, and symptoms such as snoring, snorting, and pauses in breathing.

Studies show that obstructive sleep apnea is associated with stroke. Whether other sleep orders are linked to stroke remains unknown.

Knowing more about how sleep problems may affect stroke risk could aid the development of preventative strategies.

Recently, researchers investigated the link between sleep problems and the incidence of acute stroke.

They found that the more sleep problems individuals had, the more likely they were to experience stroke. The study paper appears in the journal Neurology.

Dr. Adi Iyer, a neurosurgeon and neurointerventional surgeon at Pacific Neuroscience Institute at Providence Saint John’s Health Center in Santa Monica, CA, not involved in the study, told Medical News Today that, “[w]hile there may be independent physiological changes that occur with poor sleep predisposing to stroke, it is likely that overall sleep represents an epiphenomenon of known stroke risk factors such as obesity, older age, alcohol use, etc.”

“Sleep may be a modifiable risk factor for stroke and clinicians should assess patients’ sleep quality and duration,” he added.

Sleep problems and stroke risk

For the study, the researchers analyzed healthcare data from 1,799 participants who had experienced an ischemic stroke — the most common kind of stroke, in which a blood clot blocks an artery leading to the brain.

They also analyzed data from 439 people who experienced an intracerebral hemorrhage (ICH) — bleeding in brain tissue — and 4,496 controls who were matched according to age and sex. Participants were an average of 62 years old.

Finally, the researchers asked the participants about their sleep behaviors, including sleep duration and sleep quality, in the month before experiencing their stroke.

In the end, the researchers found that multiple sleep problems were linked to increased stroke incidence.

More specifically, those who slept less than 5 hours per night were three times more likely to have a stroke than those who slept for 7 hours. Meanwhile, stroke risk was doubled for those sleeping more than 9 hours per night compared to those sleeping 7 hours.

Sleep apnea — pauses in breathing multiple times per hour — was linked to a three times higher stroke risk. Napping for an hour or more was also linked to an 88% higher stroke risk when compared to no napping at all.

The researchers also found that those who snored were 91% more likely to have a stroke than those who did not, and that those who snorted were almost three times more likely to have a stroke than those who did not.

They further found that the more sleep problems individuals had, the more likely they were to experience stroke or ICH.

“Not only do our results suggest that individual sleep problems may increase a person’s risk of stroke but having more than five of these symptoms may lead to five times the risk of stroke compared to those who do not have any sleep problems,” warns Dr. Christine McCarthy of the University of Galway in Ireland, the leading author and corresponding author of the study.

The results remained valid even after the researchers controlled for potentially confounding factors, including depression, alcohol use, and physical activity.

What do sleep experts think?

MNT spoke with Dr. Thomas Kilkenny, director of the Institute Sleep Medicine at Staten Island University Hospital, not involved in the study, to understand more about the link between sleep problems and stroke risk.

He said that 80% of adult sleep is non-REM sleep, and that during this time, the cardiovascular system is controlled by the autonomic nervous system which reduces blood pressure, heart rate, and cardiovascular strain. These factors, he noted, have a protective effect on cardiovascular health.

He added that sleep disruption, including sleep apnea, insomnia, and shift work, may impair this protective effect by reducing time spent in non-REM sleep. He added: “When this occurs, there is a decrease in the [cardiovascular] recovery but also a significant increase [in] stress on the cardiovascular system.”

“Poor sleep quality, through [a] reduction in non-REM sleep, also activates a multitude of other mechanisms including intermittent hypoxia injury, blood pressure swings, cardiac arrhythmia, inflammation, insulin resistance, stress hormone activation, and hypercoagulability, all of which have the potential to provoke cardiovascular diseases including strokes.”

– Dr. Thomas Kilkenny

Dr. McCarthy also noted that “[s]leep is increasingly being recognized as the third pillar of health, along with diet and exercise, although it has not been as thoroughly researched.”

Nevertheless, she cautioned that it is difficult to tell whether sleep problems cause stroke risk factors or vice versa.

“For example,” she noted, “increased alcohol intake may cause disruptions in sleep quality, but impairments in sleep quality may result in increased use of alcohol as a sedative. Future interventional research is required to determine causal associations.”

Study limitations

When reflecting on their study’s limitations, Dr. McCarthy noted that one factor to keep in mind is potential bias, as”people reported their own symptoms of sleep problems, so the information may not have been accurate, subject to recall and misclassification bias.”

Dr. Kilkenny added that “[t]he major limitation is that the study findings are just associations and not a direct cause and effect.”

“This means that people with poor sleep quality are more likely to have a stroke, not necessarily that poor sleep directly causes the stroke,” he said.

“Further studies are needed. Likewise having insomnia, taking long naps, or being a long sleeper may be a sign of another health disorder that could be triggering the cardiovascular disease,” noted Dr. Kilkenny.

Further implications 

When asked about the study’s implications of the study, Dr. Kilkenny said it should be an “awakening” to patients and physicians on the importance of good quality sleep.

“The study results also give physicians an incentive to inquire about sleep habits when seeing patients in the office. Sleep is rarely discussed routinely in the office and physicians may be missing an opportunity to improve their patient’s health by picking up sleep disturbances sooner,” he added.

Dr. McCarthy noted:

“Our findings suggest that sleep disturbance symptoms may represent either risk factors for stroke, and/ or their presence identifies people at increased risk of stroke. The study does not show that sleeping problems cause stroke. It only shows an association. Given our findings, future studies should look at interventions for sleep problems, and their potential to reduce stroke risk.”

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