The course of insomnia over one year: a longitudinal study in the general population in Sweden.

STUDY OBJECTIVES

The purpose of this study was to examine the course of insomnia in the general population over one year with an emphasis on prevalence, consequences, persistence, remission, and incidence of insomnia.

DESIGN

This study employed a longitudinal design with a 1-year followup. Insomnia was defined as reporting problems sleeping for 3 nights or more per week during the past 3 months, problems with daytime symptoms or daytime functioning, and difficulties with sleep onset, sleep maintenance, or early morning awakening.

PARTICIPANTS

From a randomly selected sample of the adult general population (N = 3,000; 20 to 60 years), 1,746 individuals filled out a baseline and 1-year follow-up survey.

RESULTS

The prevalence rates of insomnia were 6.8% to 9.7% at the 2 assessment points. The longitudinal analyses suggested that for 44.4% of the individuals with insomnia at baseline, insomnia was characterized by persistence (4.3% of the general population). For 56.6% of the individuals with insomnia at baseline, the condition remitted over one year (5.4% of the general population). The cumulative incidence of insomnia was 2.8% over the course of a year.

CONCLUSIONS

In summary, the results showed that insomnia is a prevalent condition in the general population associated with negative consequences and is characterized not only by persistence but also by relatively high remission and incidence.