Insomnia : Prevalence, longitudinal course and health consequences - a twelve year perspective

Abstract: The aim of this thesis is to investigate different aspects of insomnia by following a middle-aged population over a twelve-year period. In the present series of studies insomnia is defined as a complaint of either difficulties initiating sleep (DIS), difficulties maintaining sleep (DMS) or early morning awakenings (EMA).In 1983 a study of 1,870 subjects aged 45-65 years was performed, based on a questionnaire that focused on sleep and health. Twelve years later, 74.1% of the surviving study population participated in a follow-up study and answered an almost identical questionnaire. The prevalence rate of insomnia at follow-up was 20.4% with a female preponderance. Depression was the variable most consistently related to insomnia while older age was not, when a simultaneous control for the effects of age, gender, depression and anxiety was carried out. A majority of those with insomnia in 1983 also reported insomnia at follow-up. Females complaining of insomnia in 1983 had a four-fold increased risk of being depressed twelve years later independent of depression status at baseline.Mortality data were collected, and males reporting DIS ran a three-fold increased risk of coronary artery disease mortality over the twelve-year period when adjustment was made for several important risk factors. In conclusion, insomnia is a highly prevalent and long-lasting complaint and implies a risk for subsequent depression in females. Furthermore, DIS is an important risk factor for coronary artery disease mortality in males.

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