SAN ANTONIO — Chronic insomnia is an independent risk factor for all-cause mortality, conferring a threefold increased risk, according to data from the landmark Wisconsin Sleep Cohort Study.
This surprisingly robust increased risk was seen across all the major subtypes of chronic insomnia, including frequent difficulty in falling asleep, repeated awakening during the night, and waking up too early, Laurel A. Finn reported. Higher mortality also was seen for sleep maintenance insomnia marked by difficulty in getting back to sleep after awakening, she said.
These findings boost the priority level for treatment of chronic insomnia. The data provide added impetus for physicians to prescribe effective treatments for patients who complain of insomnia, even in the absence of comorbid medical or psychiatric conditions, added Ms. Finn of the University of Wisconsin, Madison.
She reported on 2,242 Wisconsin state employees, mean age 44 years, who completed at least two of the detailed sleep questionnaires mailed by investigators in 1989, 1994, and 2000. If on two or more surveys they reported insomnia symptoms more than five times in the prior month, they were classified as having chronic insomnia.
By this definition, 46% of the survey participants had chronic insomnia. Chronic repeated awakening was reported by 26% of participants, while each of the other three subtypes of chronic insomnia occurred in 15%-18%.
A total of 128 participants died during a mean follow-up of 19 years. The all-cause mortality rate was 8.6% in participants with chronic insomnia and 2.6% in those with no insomnia.
In a multivariate analysis adjusted for potential confounders, including age, gender, smoking, sleep-disordered breathing, alcohol use, asthma, cardiovascular disease, diabetes, depression, chronic obstructive pulmonary disease, and history of stroke, chronic insomnia remained independently associated with a threefold increased risk of mortality. Each of the subtypes of chronic insomnia was associated with a 2.5- to 3.3-fold increased risk.
Possible explanations for the increased mortality among individuals with chronic insomnia even after controlling for medical and psychiatric comorbidities include the well-documented increased accident rates associated with chronic insomnia, as well as decreased quality of life.
Chronic sleeplessness also could hamper recovery from major illness or injury, she observed.
The Wisconsin Sleep Cohort Study is funded by the National Institutes of Health. Ms. Finn reported having no financial conflicts.