Objectives: To investigate the prevalence of and the factors associated with daytime sleepiness occurring every or almost every day.
Design: A cross-sectional, questionnaire survey.
Subjects: A total of 11,354 adults (aged 33-60 years) representative of the Finnish population.
Main outcome measures: Frequency of daytime sleepiness, naps and sleep attacks; occurrence of emotion-associated muscle weakness, sleep debt, insomnia, sleep apnoeas and type of snoring; Beck Depression Inventory score; and the use of hypnotics and tranquillisers.
Results: A total of 11.0% of women and 6.7% of men suffered from daytime sleepiness every or almost every day. Amongst those with sleepiness (n = 1,026) 19.5% of women and 42.3% of men reported snoring > or = 3 nights per week, 25% had scores suggesting moderate to severe depression, 11% used hypnotics or tranquilizers on more than 180 days per year, and 9% reported insufficient sleep. Insomnia at least every other day was reported by 20.7% of women and by 28.6% of men. Amongst those with sleepiness, narcolepsy was found in 0.3%, with the diagnosis confirmed in a sleep laboratory evaluation.
Conclusions: Daytime sleepiness occurring daily or almost daily is most often associated with depression, insomnia and sleep-disordered breathing. In most cases, indications of the cause of sleepiness can be obtained by using simple screening questions.