Daytime Sleepiness an Independent Risk Factor for Stroke

Caroline Cassels

February 22, 2008

February 22, 2008 (New Orleans, Louisiana) — Unintentional regular daytime dozing can more than quadruple stroke risk in elderly patients and significantly increase their risk for other vascular events.

Presented here at the American Stroke Association's International Stroke Conference 2008, these latest findings from the Northern Manhattan Study (NOMAS), a prospective study of stroke and stroke risk factors in a multiethnic population, showed individuals with excessive daytime sleepiness had a 4.5-fold increased risk for stroke compared with their counterparts who did not doze off during the day.

According to study investigator Bernadette Boden-Albala, PhD, from Columbia University, in New York, this is the first large prospective study to show that daytime sleepiness is an independent risk factor for stroke and all vascular events.

"At this point it is fair to say doctors don't fully appreciate the impact of sleep disturbance on vascular disease. However, these results clearly indicate it is very important," Dr. Boden-Albala told Medscape Neurology & Neurosurgery.

Previous research has linked poor or diminished quality of sleep to an increased risk for vascular events, including stroke. However, prospective studies are limited and have included only populations diagnosed with a sleep disorder such as sleep apnea.

The researchers used the Epworth Sleepiness Scale (ESS), which measures daytime sleepiness, and 2 nighttime sleep questions about snoring and choking as a marker of sleep disturbance. They then examined the risk for stroke and other vascular events.

In 2004 investigators began collecting daytime dozing data using the ESS as part of the annual NOMAS follow-up. Subjects, who were stroke-free at study entry, were divided into 3 groups: no dozing, some dozing, and significant dozing.

A total of 2153 subjects were included in the final analysis. Of these, 44% reported no dozing, 47% reported some dozing, and 9% reported significant dozing. At 2-year follow-up investigators found there had been 40 strokes and 127 vascular events.

Unexpectedly High Risk

After adjusting for age, race/ethnicity, sex, education, systolic blood pressure, diabetes, obesity, and physical activity, investigators found unexpectedly high risk the among "some dozing" and "significant-dozing" groups.

"At 2 years of follow-up we really didn't expect to see any effect, but, boy, did we see something. I think it is really significant that in this very short period of time we saw this strong an effect," said Dr. Boden-Albala.

Compared with those who reported "no dozing," individuals reporting "significant dozing" had a 4.5-fold increased risk for stroke and those who reported "some dozing" had a 2.6-fold increased stroke risk.

Further adjusted analyses revealed daytime sleepiness also markedly increased the risk for all vascular events, with a 60% increased risk among those who reported some dozing and a 2.6-fold increased risk in the "significant dozing" group.

One of the "troubling" aspects of these findings, said Dr. Boden-Albala, is the fact that more than half of the study population (56%) had sleep disturbance. At this point, she said, it is not clear whether sleep apnea is driving the observed risk, but what is clear is the importance of sleep on vascular health.

"People need to speak to their physician about sleep, and physicians need to screen for sleep disturbances. An initial assessment can be something as simple as the Epworth scale. If patients are moderately or significantly dozing, physicians need to think about sending them for further evaluation," she said.

Commenting on the study for Medscape Neurology & Neurosurgery, George Howard, DrPH, from the University of Alabama at Birmingham, also said the findings reinforce the need for physicians to assess patients' sleep quality.

"You can't tell whether a patient has a fever if you don't take their temperature, and the same principal applies to sleep disturbance. Physicians need to ask their patients about sleep, and patients need to be made aware of the importance of sleep on their health and understand that if they have a problem with sleep they should raise the issue with their doctor," he said.

The study was funded by the National Institute of Neurological Disorders and Stroke.

American Stroke Association International Stroke Conference 2008: Abstract 94. Presented February 21, 2008.

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