Prevalence of reported sleeplessness in northern Norway in relation to sex, age and season.

As part of a comprehensive population health survey in the municipality of Tromsø, north of the Arctic Circle, men between 20 and 54 years and women between 20 and 49 years were presented a questionnaire containing questions about sleeplessness and its possible association with season. Of the 14,667 respondents, 41.7% of the women and 29.9% of the men said they were sometimes bothered by insomnia. Insomnia not associated with any special time of the year was reported by 16.9% of women and 16.2% of men; insomnia in the "dark period" (midwinter insomnia) was reported by 17.6% of women and 9.0% of men; insomnia in the midnight-sun period or in spring or autumn was much less common. Difficulty falling asleep was the most common type of insomnia, especially in winter and summer. Overall, the frequency of insomnia increased with increasing age, but with some notable differences with regard to type (initial insomnia showed little relation to age, whereas middle and late insomnia increased markedly with age) and seasonal type (insomnia in the midnight-sun period decreased with age, whereas the other seasonal types increased with age).