WEDNESDAY, March 11 (HealthDay News) -- Insomnia is a persistent condition for many people, a new study finds.

Canadian researchers found that about 75 percent of those with insomnia experience the condition for at least a year, and almost half experience it for three years.

Over a three-year span, the researchers evaluated insomnia persistence, remission and relapse in 388 people, who averaged about 45 years old. They compared 269 people with insomnia symptoms with 119 people who had what they termed insomnia syndrome -- meaning they had insomnia symptoms at least three nights a week for at least a month, causing substantial distress or daytime drowsiness.

"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," wrote the researchers, who were from Laval University in Quebec.

People with insomnia syndrome had a higher insomnia persistence rate (66.1 percent) than those with insomnia symptoms (37.2 percent). About 54 percent of everyone in the study went into insomnia remission, but 26.7 percent of them eventually relapsed.

Of the 269 people with insomnia symptoms at the start of the study, 38.4 percent were classified as good sleepers after a year, 48.7 percent still had insomnia symptoms, and 12.9 percent had insomnia syndrome. Among the 119 people with insomnia syndrome at the start of the study, 17 percent were good sleepers after a year, 37 percent still had symptoms of insomnia, and 46 percent still had insomnia syndrome.

The findings were published in the March 9 issue of Archives of Internal Medicine.

"This study provides preliminary evidence to better understand the natural course of insomnia," the authors wrote. "Additional studies are needed, however, to identify moderating and mediating factors of persistence, remission and relapse."

About 30 percent of adults report symptoms of insomnia, and 6 percent to 10 percent meet diagnostic criteria for an insomnia disorder, according to background information in the study. Insomnia risk factors include being female, older, having anxiety or depression, and experiencing pain. Insomnia has been linked to depression, hypertension, disability, work absenteeism and higher health-care costs.

More information

The U.S. National Heart, Lung, and Blood Institute has more about insomnia.

-- Robert Preidt

SOURCE: JAMA/Archives journals, news release, March 9, 2009

Last Updated: March 11, 2009

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