Insomnia is a symptom of a sleeping disorder characterized by persistent difficulty falling asleep or staying asleep despite the opportunity.

Several factors such as being female, increasing age, having anxiety or depression and experiencing pain from medical conditions have been associated with insomnia.

The condition has been linked to higher health care costs, work absenteeism, disability and higher risk of hypertension and depression.

For the study, Charles M Morin, PhD, of Université Laval and Centre de recherche Université Laval—Robert Giffard, Québec, Canada, and colleagues evaluated insomnia persistence, remission and relapse in 388 adults (average age 44.8) over a course of three years.

Individuals with an insomnia syndrome (insomnia symptoms at least three nights per week for at least one month causing substantial distress or daytime impairment) at the beginning of the study were compared to those with insomnia symptoms to examine the course of initial severe sleep difficulties.

"Of the study sample, 74 per cent reported insomnia for at least one year and 46 per cent reported insomnia persisting over the entire three-year study," the authors write.

The group with initial insomnia syndrome had a higher persistence rate than the group with symptoms of insomnia (66.1 per cent vs 37.2 per cent), respectively.

About fifty-four per cent of participants went into insomnia remission; however, 26.7 per cent of them eventually experienced relapse.

"Individuals with subsyndromal insomnia [insomnia symptoms] at baseline were three times more likely to remit than worsen to syndrome status, although persistence was the most frequent course in that group as well," the authors said.

Of the 269 individuals with baseline symptoms of insomnia, after one year 38.4 per cent were classified as good sleepers, 48.7 per cent still had insomnia symptoms and 12.9 per cent had insomnia syndrome.

Results were similar after the second and third year of follow-up. Of the 119 participants with insomnia syndrome at the beginning of the study, 17 per cent were good sleepers after one year, while 37 per cent had symptoms of insomnia and 46 per cent remained in the insomnia syndrome group.