Friday, September 17, 2010

Insomnia, Sleep Duration, and Mortality

In the September edition of the Sleep Journal, there is an article about the association of insomnia, sleep duration, and insomnia. The authors followed adult men and women to assess death rates. The study participants were assessed with a comprehensive sleep history and physical exam and one night in the sleep laboratory. Insomnia was defined subjectively as an insomnia complaint that lasted for one year. Sleep duration was defined as short if it lasted less than 6 hours per patient's report.

The results showed that in men, the mortality rate was increased for insomniacs with short sleep duration and this was independent of age, race, obesity, alcohol consumption, smoking, obstructive sleep apnea, or depression. The effect was not mitigated by the presence of high blood pressure or diabetes.

There was no increased mortality in women, whether or not they were short sleepers or had insomnia. Also, the association with sleep duration was only for the subjective report, and not based on the duration of sleep measured objectively in the sleep lab.

This study purports to be the first one to link insomnia with mortality. However, the average follow up was 14 years in the men, meaning their sleep study was done at a time when only airflow was routinely monitored. This means that nasal pressure transducers were not used, and therefore sleep apnea could have been present in these men. Sleep apnea is more prevalent in men which could explain why the mortality rate was increased for men and not women.

I'll concede that some patients with insomnia can have a revved up nervous system, referred to as hyperarousal. This, theoretically, could increase cardiovascular disease. But the results of this study do not prove that insomnia by itself increases mortality. Objective monitoring of sleep duration at home over extended periods of time will help answer this question more completely.

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