"Of the study sample, 74 percent reported insomnia for at least one year and 46 percent 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 percent vs. 37.2 percent), respectively. About fifty-four percent of participants went into insomnia remission; however, 26.7 percent 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 note.
Of the 269 individuals with baseline symptoms of insomnia, after one year 38.4 percent were classified as good sleepers, 48.7 percent still had insomnia symptoms and 12.9 percent 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 percent were good sleepers after one year, while 37 percent had symptoms of insomnia and 46 percent remained in the insomnia syndrome group.
"This study provides preliminary evidence to better understand the natural course of insomnia. Additional studies are needed, however, to identify moderating and mediating factors of persistence, remission and relapse," the authors conclude. "Improved understanding of the long-term course of persistent insomnia would be helpful to guide the development of effective public health prevention and intervention programs to avert long-term negative outcomes."