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SLEEP 2012 MEETING
Short Sleep May Increase Stroke Risk
2012;20(7):1,17.
BOSTON?Regularly sleeping for less than six hours quadruples the rate of stroke symptoms among middle-aged and older persons with a normal BMI and a low risk of sleep-disordered breathing, according to a study that was presented at the 26th Annual Meeting of the Associated Professional Sleep Societies.

Researchers found no association between a six-hour sleep duration and stroke symptoms among overweight and obese persons.

Unadjusted results indicated that a sleep duration of less than six hours as well as a sleep duration of nine hours or more were strong predictors of stroke symptoms, but the predictive strength of these factors decreased when the data were adjusted, said Megan Ruiter, PhD, a postdoctoral fellow in preventive medicine at the University of Alabama at Birmingham. She and her colleagues noted a significant interaction between sleep duration and BMI, however.

Sleep duration of less than six hours was strongly associated with a greater incidence of stroke symptoms in the fully adjusted data model for participants with normal BMI. Sleep loss is associated with endothelial dysfunction, and it could increase stroke risk by this mechanism. ?Perhaps this short sleep duration in these relatively healthy individuals might be a precursor to more traditional stroke risk factors down the road,? said Dr. Ruiter.
Analysis of Data From the REGARDS Study
Dr. Ruiter and her colleagues analyzed data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study to determine whether sleep duration predicted self-reported stroke symptoms among individuals at low risk for sleep-disordered breathing. The longitudinal, nationwide cohort study encompassed 30,239 participants age 45 and older. The investigators collected self-reports of each person?s average sleep duration. At six-month intervals, the researchers obtained subjects? self-reported stroke symptoms.

A total of 5,666 participants had no history of stroke, transient ischemic attack, or stroke symptoms and were not at high risk for sleep-disordered breathing. Participants? mean age was 61, and about a third were African American. Most of the individuals in the study were employed. Average follow-up time was two years, and 244 participants reported at least one stroke symptom.

Dr. Ruiter?s team estimated the hazard ratios predicting time from measurement of sleep duration to first stroke symptom. Models were adjusted for demographic information, Framingham stroke risk factors, depressive symptoms, anxiety, and various health behaviors such as physical activity and diet quality.

Sleep Fragmentation?s Effect on Stroke Symptom Risk Is Unclear
In the fully adjusted model, participants of normal BMI who slept for less than six hours had a fourfold greater risk for stroke symptoms, compared with normal-weight participants who slept for seven to eight hours. The analysis of the results suggests that improving sleep might lower stroke risk in persons with normal BMI, said Dr. Ruiter. ?It might be important to increase physician awareness? of sleep problems, she added.

One of the study?s limitations is that most of the sample population was employed. ?People who were not employed, or [who were] retired or homemakers, likely didn?t answer the sleep duration question, because it was asking about how much sleep they would get on their work and nonwork days,? noted Dr. Ruiter.

Because the study asked for participants? perception of their sleep, it is unclear whether participants reported their total amount of sleep, or their total amount of time in bed, attempting to sleep. The researchers need to analyze the data further to determine whether the increased stroke risk is associated with short sleep or sleep fragmentation, according to Dr. Ruiter.

More evidence is required to validate the results, and Dr. Ruiter and her colleagues will continue to follow the participants in the REGARDS study and look at actual stroke events.

?Erik Greb
Suggested Reading
Eguchi K, Hoshide S, Ishikawa S, et al. Short sleep duration is an independent predictor of stroke events in elderly hypertensive patients. J Am Soc Hypertens. 2010 Sep-Oct;4(5):255-262.
Matthews KA, Strollo PJ Jr, Hall M, et al. Associations of Framingham risk score profile and coronary artery calcification with sleep characteristics in middle-aged men and women: Pittsburgh SleepSCORE study. Sleep. 2011;34(6):711-716.