Types of sleep and risk of mortality

Oct 2 2007

The first study to assess the stability of three aspects of sleep behavior in relation to long-term mortality finds an increased risk of mortality in short sleep, long sleep and frequent use of medications, according to a study published in the October 1 issue of the journal SLEEP.

The study, authored by Christer Hublin, MD, PhD, of the Finnish Institute of Occupational Health in Helsinki, Finland, focused on the responses of 21,268 twins to questionnaires administered in 1975 and 1981. The subjects were categorized as follows:

• Short sleepers (less than seven hours)
• Average sleepers
• Long sleepers (more than eight hours)
• Sleeping well
• Sleeping fairly well
• Sleeping fairly poorly/poorly
• Not users of hypnotics and/or tranquilizers
• Infrequent users of hypnotics and/or tranquilizers
• Frequent users of hypnotics and/or tranquilizers

According to the results, significantly increased risk of mortality was observed both for short sleep in men (+26 percent) and in women (+ 21 percent), and for long sleep (+24 percent and +17 percent respectively), and also frequent use of hypnotics/tranquilizers (+31 percent in men and +39 percent in women). The effect of sleep on mortality varied between age groups, with strongest effects in young men.

Between 1975 and 1981, sleep length and sleep quality changed in about one-third of the population. In men, there was a significant increase for stable short (1.34) and stable long (1.29) sleep for natural deaths, and for external causes in stable short sleepers (1.62).

“This study found an association between sleep behavior (most notably in sleep length) and mortality. The exact mechanisms remain unclear, and they should be assessed in experimental settings and other longitudinal studies. Morbidity and functional limitations as less severe outcomes should also be considered. Although the effect of sleep on mortality is fairly modest compared to, for example, smoking or components of the metabolic syndrome, it is still of considerable significance as it is associated with several common disorders such as cardiovascular diseases and diabetes. Optimizing sleep – in addition to disorder-specific treatment – could improve prognosis in these disorders. Our results add evidence to the association between sleep and health outcomes,” said Dr. Hublin.

Those who think they might have a sleep disorder are urged to discuss their problem with their primary care physician, who will issue a referral to a sleep specialist.

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