A study in the journal SLEEP suggests the risk of death is more than two times higher in older adults who have sleep apnoea and report struggling with excessive daytime sleepiness.
Results of adjusted proportional hazards modelling show that older adults with moderate to severe sleep apnoea who reported struggling with excessive daytime sleepiness at baseline were more than twice as likely to die (hazard ratio = 2.28) as subjects who had neither problem.
The risk of death was insignificant in older adults with only excessive daytime sleepiness (HR = 1.11) or sleep apnoea (HR = 0.74). Participants had a mean age of 78 years at baseline, and about 55% (n = 160) died during an average follow-up period of 14 years.
"Excessive daytime sleepiness, when associated with sleep apnoea, can significantly increase the risk of death in older adults," said principal investigator and lead author Dr Nalaka S. Gooneratne, assistant professor of medicine in the University of Pennsylvania Health System in the US.
"We did not find that being sleepy in and of itself was a risk. Instead, the risk of increased mortality only seemed to occur when sleep apnoea was also present."
Gooneratne added that both daytime sleepiness and sleep apnoea are common problems, with sleep apnoea affecting up to 20% of older adults.
According to the American Academy of Sleep Medicine, the most common form of sleep apnoea is obstructive sleep apnoea, which occurs when soft tissue in the back of the throat collapses and blocks the upper airway during sleep. Older adults also are at risk for central sleep apnoea, which involves a repetitive absence of breathing effort during sleep, caused by a dysfunction in the central nervous system or the heart.
Only 4% of participants had central sleep apnoea, and there was no meaningful change in the results when they were excluded from the analysis.
The study involved 289 adults with neither dementia nor depression who were recruited from the community - 74% were female. About half (n = 146) had significant levels of excessive daytime sleepiness at baseline, reporting that they felt sleepy or struggled to stay awake during the daytime at least three to four times a week.
Sleep apnoea was measured objectively by one night of polysomnography in a sleep lab. For analysis, participants were included in the sleep apnoea group only if they had an apnoea-hypopnoea index of 20 or more breathing pauses per hour of sleep, which represents a moderate to severe level of sleep apnoea.
According to the authors, the mechanism by which sleep apnoea and excessive daytime sleepiness increase the risk of death is unclear. They suspect that inflammation may be involved, which could increase the risk of other medical problems such as hypertension. It also remains to be seen if treatment reduces the risk of death.
"Future research is needed to assess whether treating the sleep apnoea can reduce mortality," said Gooneratne.
The treatment of choice for OSA is CPAP therapy, which provides a steady stream of air through a mask that is worn during sleep. This airflow keeps the airway open to prevent pauses in breathing and restore normal oxygen levels. - (EurekAlert!, April 2011)