Though it's often blamed on not getting a good night's rest, feeling excessively sleepy during the day could be an indicator of health problems such as depression and diabetes, a study published in The Journal of Clinical Endocrinology & Metabolism shows.
"Excessive daytime sleepiness is commonly assumed to be the result of disturbed or inadequate sleep," wrote Dr. Edward Bixler, a psychology professor at Pennsylvania State University, and colleagues.
Most often, daytime sleepiness is blamed on sleep apnea, which occurs when people stop breathing for periods of 10 seconds or more, causing them to wake repeatedly during the night and preventing deep, restful sleep.
But Bixler's study shows other factors may make it difficult for some people to keep their eyes open during the day.
The study was conducted in two phases. In the first, 16,583 people between the ages of 20 and 100 took part in telephone surveys to assess whether they had excessive daytime sleepiness. They were asked questions such as "Do you feel drowsy or sleepy most of the day but manage to stay awake?" and "Do you have any irresistible sleep attacks during the day?" Participants were also asked about their health status, including whether they were being treated for depression, diabetes, allergies, and other conditions.
Nearly 9% of participants reported experiencing excessive daytime sleepiness, with a higher prevalence among those below the age of 30 and above the age of 75. The researchers speculate that this is due to too few hours of sleep among the younger population and health problems among the elderly.
In the second phase of the study, 1,741 of the survey participants attended a sleep lab, where they were monitored for eight hours while sleeping in a quiet light- and temperature-controlled room. They also completed a comprehensive sleep history and physical examination. There were no significant differences in age, body mass index (BMI), and prevalence of sleep disorders between the phase two participants and the overall study population.
After analyzing data collected in phase two of the study, the researchers found a weak relationship between sleep apnea and excessive daytime sleepiness. "It appears that EDS (excessive daytime sleepiness) is more strongly associated with mood factors (e.g. depression) as well as metabolic factors (obesity and/or diabetes)," the researchers concluded. Depression was found to be the biggest risk factor for daytime sleepiness, followed by BMI, age, typical sleep duration, diabetes, and smoking. Sleep apnea ranked last.
"Our findings suggest that patients with a complaint of excessive daytime sleepiness should be thoroughly assessed for depression and obesity/diabetes independent of whether sleep-disordered breathing is present," the authors said.
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