Obesity, depression too make us feel 'drowsy' during day

It's not only sleep deprivation, but obesity and depression too play role in making us feel drowsy and sleepy all the time.

According to Penn State College of Medicine researchers as much as 30 percent of the general population experiences excessive daytime sleepiness (EDS), daytime drowsiness or sleepiness occurring throughout the day that can include irresistible sleep attacks.

Feeling overly tired during the day can reduce job productivity and increase errors and absenteeism and may lead to more serious issues like automobile accidents.

Previous research has associated EDS with obesity, depression and sleep apnea, but the new study is the first to use physiologic sleep data to infer causation and investigate mechanisms. It is also the first observational study of EDS over several years.

The researchers measured self-reporting of EDS at baseline and again an average of 7.5 years later in 1,395 men and women. Study participants completed a comprehensive sleep history and physical examination and were evaluated for one night in a sleep laboratory. The researchers also recorded sleep, physical and mental health problems and substance use and determined whether participants were being treated for physical and mental health conditions.

Assistant professor Julio Fernandez-Mendoza said that obesity and weight gain predicted who was going to have daytime sleepiness. Moreover, weight loss predicted who was going to stop experiencing daytime sleepiness, reinforcing the causal relationship.

The association between body mass index and sleepiness was independent of sleep duration, meaning obese people may be tired during the day no matter how much they sleep at night.

Obesity is also associated with sleep apnea, a condition in which breathing pauses occur during sleep. A hallmark of sleep apnea is daytime sleepiness. Although it may seem logical to assume that sleep apnea causes fatigue in obese people, the study refutes this.

Fernandez-Mendoza said that the mechanism that may be playing a role in the process could be hyperarousal, which is simply going to bed and being too alert; in other words, people with depression felt fatigued but did not necessarily fall asleep during the day.

The researchers also found that a minority of people with EDS have a physiologic sleepiness disorder of the central nervous system. They actually sleep longer than average at night, in part because they fall asleep faster than normal.

Taken together, the findings indicate that a one-size-fits-all approach to treating EDS-most often a prescription for sleeping pills and more sleep-will fail in the long term.

The study is published in the journal SLEEP.