This article examines the natural history of excessive daytime sleepiness (EDS). In the article, the authors explain that EDS affects about 30% of the general public. They also explain that EDS is associated with certain psychiatric, metabolic, and sleep disorders. I would add that EDS is also a result of insufficient amount of sleep and sedating medications.
In this study, participants had a comprehensive sleep history and physical exam along with an in-lab overnight sleep study at baseline. No daytime sleepiness study, called the Multiple Sleep Latency Test (MSLT), was performed - sleepiness was only determined subjectively. Sleep apnea was defined at a cutoff that is standard for moderate severity - it's not explained why they did not include those with mild sleep apnea, who could be just as sleepy as more severe levels. Finally, follow up was only through telephone interview - no repeat sleep study or physical examination was done. The follow up was 7.5 years after the baseline evaluation, on average. Therefore, there are some important limitations to this study.
Incident EDS was defined as those who had no EDS at baseline but did have it at follow up. Remitted EDS meant those that had EDS at baseline, but not at follow up. And persistent EDS meant those that had EDS at both baseline and follow up. Results showed that incident EDS was 8.2%, and was more commonly associated with male gender, non-Caucasian race, and younger and older age. Depression, sleep apnea, obesity, and diabetes were also associated with incident EDS. Sleep duration less than 5 hours or more than 8 hours was associated with incident EDS. However, insomnia was not associated with incident EDS. Snoring was related to incident EDS, especially in those with sleep apnea.
The persistent EDS rate was 38%, whereas 62% had remitted EDS. Persistent EDS was associated strongest with anemia and insomnia. Individuals with incident or persistent EDS gained significantly more weight when compared to those without EDS. Also, individuals with remitted EDS gained significantly less weight compared to those without EDS.
The authors concluded that obesity, depression, and sleep disorders should be a public health priority to improve EDS.