Aug. 12, 2005 — Depression may be a leading cause of excessive daytime sleepiness, new research shows.

Pennsylvania State University psychiatry professor Edward Bixler, PhD, and colleagues report the finding in The Journal of Clinical Endocrinology & Metabolism.

“Excessive daytime sleepiness is commonly assumed to be the result of disturbed or inadequate sleep,” they write.

The daytime-drowsiness problem is often viewed as a sign of sleep apnea, in which a person regularly stops breathing for 10 seconds or longer during sleep. Bixler’s study shows that other culprits may be even bigger causes of excessive daytime sleepiness.

Researchers’ Recommendation

The researchers recommend that people seeking help for excessive daytime sleepiness be screened for depression, obesity, and diabetes.

“These data indicate that when diagnosing a case with a complaint of excessive daytime sleepiness, sleep disturbance (e.g. due to sleep apnea) should not be considered the only cause,” write Bixler and colleagues.

“It appears that excessive daytime sleepiness is more strongly associated with mood factors (e.g. depression) as well as metabolic factors (e.g. obesity and/or diabetes),” they write.

Sleep Study

First, the researchers did phone interviews with more than 16,000 men and women from central Pennsylvania. Nearly 9% of the group had excessive daytime sleepiness. Excessive daytime sleepiness was seen equally among men and women.

It’s been reported that up to 12% of the general public has excessive daytime sleepiness and that excessive daytime sleepiness is the No. 1 problem mentioned by sleep clinic patients, states a news release from The Endocrine Society.

Next, 741 men and a thousand women who had taken the survey spent a night at Penn State’s sleep lab. Participants were fully wired, so researchers could monitor them as they slept (or tossed and turned).

Other data included smoking habits, diabetes, body mass index [BMI], and hours of nightly sleep.

Biggest Factor: Depression

After crunching the numbers, depression was the No. 1 risk factor for excessive daytime sleepiness. BMI came second. Typical sleep duration was third, followed by diabetes, smoking, and, finally, sleep apnea.

“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,” write the researchers.