Jim Kling

July 14, 2010

July 14, 2010 (San Antonio, Texas) — Chronic insomnia is associated with an approximately 2-fold increased risk for all-cause mortality, according to a study from the Wisconsin Sleep Cohort, which was presented here at SLEEP 2010: Associated Professional Sleep Societies 24th Annual Meeting.

The study looked at the association between chronic insomnia and mortality rate, independent of health conditions. Subjects were drawn from participants in the Wisconsin Sleep Cohort Study who completed 3 mailed surveys in 1989, 1994, and 2000. Surveys asked about insomnia-related topics such as difficulty falling asleep, difficulty getting back to sleep, repeated awakening, and early arousal. Respondents marked symptoms as frequent (≥5 times per month) or not frequent (<5 times per month). They were considered to have chronic insomnia if they reported symptoms on at least 2 surveys.

The researchers, led by Laurel Finn, MS, a biostatistician at the University of Wisconsin School of Medicine in Madison, determined all-cause mortality by examining a social security death index in June 2009. They used Cox proportional hazards regression to estimate mortality hazard ratios. These were adjusted for body mass index, age, sex, and chronic conditions that patients said their physicians had diagnosed, including emphysema, chronic bronchitis, angina, coronary heart disease, heart attack, stroke, hypertension, and diabetes.

Among the 1872 participants, Ms. Finn and colleagues recorded 74 deaths. Patients who reported insomnia in at least 2 surveys had an adjusted hazard ratio of 2.1 (95% confidence interval [CI], 1.2 - 3.5), compared with participants not reporting insomnia.

The researchers also compared mortality hazard ratios for specific symptoms reported by patients in at least 2 surveys with those in patients who reported no symptoms in all surveys. The mortality hazard ratio for difficultly falling asleep was 1.9 (95% CI, 0.9 - 4.1), for repeated awakening was 3.2 (95% CI, 1.8 - 5.7), for difficulty getting back to sleep was 1.8 (95% CI, 0.9 - 3.4), and for early arousal was 2.4 (95% CI, 1.2 - 4.5).

"Sleep duration has been linked to (increased) mortality, and a lot of insomniacs have short sleep duration. We wondered if this could be one of the mechanisms by which short sleep duration leads to mortality," Ms. Finn, who presented the study, told Medscape Medical News.

The ongoing study has a population-based cohort, which allowed researchers to examine the natural history of participants. "We've been studying these people for 20 years, and we have a lot of data on them," Ms. Finn noted.

The study is preliminary, and the next step is to examine how insomnia affects health outcomes in comorbid conditions. "People with insomnia are fatigued. [Higher mortality could result] if they have a chronic condition and they don't follow-up on treatment [because of the fatigue]," said Ms. Finn.

The findings should prompt patients and physicians to take insomnia more seriously, Ms. Finn said. "People often look at [insomnia] as a nuisance. This [research] is saying, this needs to be taken seriously. And doctors need to look for the root causes of insomnia. There are some new pharmacotherapies that work on specific kinds of insomnia, whether it's maintaining sleep, falling asleep, or behavioral [issues]. We need to look at those root [causes] and take them seriously," said Ms. Finn.

The data confirm what has generally been suspected, according to David Schulman, MD, chief of pulmonary critical care services at Emory Hospital in Atlanta, Georgia, who attended the session. "It's much more cleanly structured data [than previous studies], and the participants have been very well characterized. It reaffirms our belief that insomnia is bad and we should be looking into it more," Dr. Schulman told Medscape Medical News.

It remains to be seen whether insomnia causes increased mortality or whether serious underlying conditions are causing insomnia. "One would hope that by treating the insomnia [the patient would have an improved outcome]. It's theoretical, but certainly worth investigating," Dr. Schulman added.

The study did not receive commercial support. Ms. Finn and Dr. Schulman have disclosed no relevant financial relationships.

SLEEP 2010: Associated Professional Sleep Societies 24th Annual Meeting: Abstract 0607. Presented June 7, 2010.

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