Objectives. To investigate the prevalence of and the factors associate
d 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. Ma
in outcome measures. Frequency of daytime sleepiness, naps and sleep a
ttacks; 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 eve
ry or almost every day. Amongst those with sleepiness (n = 1026) 19.5%
of women and 42.3% of men reported snoring greater than or equal to 3
nights per week, 25% had scores suggesting moderate to severe depress
ion, 11% used hypnotics or tranquilizers on more than 180 days per yea
r, and 9% reported insufficient sleep. Insomnia at least every other d
ay was reported by 20.7% of women and by 28.6% of men, Amongst those w
ith sleepiness, narcolepsy was found in 0.3%, with the diagnosis confi
rmed in a sleep laboratory evaluation. Conclusions. Daytime sleepiness
occurring daily or almost daily is most often associated with depress
ion, insomnia and sleep-disordered breathing. In most cases, indicatio
ns of the cause of sleepiness can be obtained by using simple screenin
g questions.