Sleep Disorders

15 June 2009

Sleep quality affects death risk

Poor quality sleep - whether from insomnia, sleep fragmentation, or nightmares - is associated with increased risk of death.

Poor quality sleep - whether from insomnia, sleep fragmentation, or nightmares - is associated with increased risk of death.

This is according to several presentations this week in Seattle at SLEEP 2009, the 23rd Annual Meeting of the Associated Professional Sleep Societies.

One study, conducted at Penn State College of Medicine in Hershey, Pennsylvania, suggests that insomnia may be as hazardous as obstructive sleep apnoea.

Insomnia causes increased stress levels
"Insomnia with objective short sleep duration is associated with an activation of the stress system, that is, higher secretion of cortisol and increased risk of high blood pressure," said lead author Dr Alexandros Vgontzas. He and his associates examined the effects of insomnia that persisted for at least 1 year, and objective short sleep duration on mortality.

The subjects included 1741 randomly selected men and women. During 14 years of follow-up among men, the mortality rate was 19.6%. Among women, who were followed for 10 years, the mortality was 10.3%.

Compared with men who had normal sleep patterns and sleep durations of at least 6 hours, men with insomnia and a shorter duration of sleep had mortality risks that were up to 5-times greater. While mortality risk was also increased among women with similar characteristics, the association was not statistically significant.

"The longer follow-up of men may explain why we did not have the same finding in women," Vgontzas. "Another possibility is that men are more vulnerable physically to this type of insomnia, that is, insomnia associated with objective short sleep duration."

Insomnia should be “medical priority”
Because "insomnia with objective sleep duration (of less than 6 hours) has significant medical consequences similar to sleep apnoea, this type of insomnia should become a medical priority in terms of its detection and treatment," he said. "At this point there are no studies that have assessed which type of treatment -- medication vs. psychotherapy vs. a combination of the two -- is more effective," he added.

Another study assessed sleep duration using actigraphy, a small instrument worn on the wrist that measures body movement and detects patterns based on activity used to evaluate sleep-wake cycles. The investigators found that sleeping less than 5 hours per night increased the risk of death among elderly women, but not among elderly men.

Sleep fragmentation also a risk factor
Dr K L Stone at California Pacific Medical Center in San Francisco and co-investigators monitored 3052 women (average age of 83.6 years) and 3055 men (average age 76.4 years) for at least three 24-hour periods.

Compared with women who slept at least 8 hours nightly, women who slept fewer than 5 hours had a significantly higher risk of death over 4.2 years of follow-up. Men who got fewer than 5 hours of sleep per night also had an increased mortality risk, but this was not statistically significant, which, again may be related to study conditions.

Based on data from the Sleep Heart Health Study, researchers led by Dr Alison M Laffan, formerly at Johns Hopkins University, Baltimore, and now at California Pacific Medical Center, have identified sleep fragmentation as another risk factor.

Included were 5614 subjects who underwent overnight polysomnography, in which brain wave activity is observed overnight during various phases of sleep, and were then followed for 8 years. The authors defined sleep fragmentation using an index of the number of sleep stage transitions per hour of sleep.

When transition types were considered individually, going from being awake to non-REM sleep and from non-REM sleep to being awake were tied to significantly higher mortality. "Other transition types decreased the odds of death; however, the decrease was observed only when the number of transitions was (less than) 1 per hour of sleep," the researchers found.

Correlation between nightmares and depression
Findings from a fourth study indicate that, among severely depressed individuals, nightmares - but not insomnia - were associated with elevated suicidal symptoms.

Principal investigator Dr Rebecca Bernert, at Florida State University, and colleagues studied 82 adults who sought emergency psychiatric evaluation and completed symptom questionnaires.

The investigators found that only scores for disturbing dreams and nightmares were independent predictors of suicidal thinking.

Thus, the researchers conclude, "a more thorough assessment of sleep in acutely ill patients is warranted, and may provide an important opportunity for intervention." –(Karla Gale, Reuters Health, June 2009).

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Dr Alison Bentley is a general practitioner who has consulted in sleep medicine and sleep disorders, in both adults and children of all ages, for almost 30 years. She also researches and publishes on a number of sleep-related topics both in formal research journals and lay publications including as editor of Sleep Matters, an educational newsletter on sleep disorders for doctors.

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