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posted: 8/15/2011 12:01 AM

Sleep apnea may have impact on dementia

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Elderly women with sleep apnea, a disorder that causes pauses in breathing during sleep, have twice the risk of cognitive impairment and dementia than those without the condition, a study found.

The research, which followed 298 elderly women for five years, suggests doctors should pay more attention to the disorder for its potential harm to the brain, according to the study's authors. The findings are published in the Journal of the American Medical Association.

Sleep apnea is a common condition in elderly people and is infrequently diagnosed and treated, said Katie Stone, a sleep disorders specialist at the California Pacific Medical Center Research Institute in San Francisco and a study author. The findings merit further study on whether treating and preventing sleep apnea can prevent or slow down the development of mild cognitive impairment and dementia, she said.

"It does appear having healthy sleep is important to health," Stone said. "The prevalence of sleep apnea definitely increases as people age. In many of these women, it's possible it has been going on for many years. It's really important when people first notice they're having problems with their sleep, they get it addressed."

Although the study only involved women, it's likely similar results may be seen in men, Stone said.

In sleep apnea, the airways from the lungs to the mouth and nose collapse during sleep, hampering the ability to inhale, the researchers said. Those with the condition usually snore and awaken many times during the night for small amounts of time, gasping for air.

It's unknown exactly how sleep apnea might lead to cognitive impairment and dementia, though healthy oxygen levels in the body are important to the brain and other organs, Stone said. Over time, chronic intermittent lack of oxygen may cause cognitive problems, Stone said.

Researchers in the study looked at 298 women without dementia whose average age was 82. The women had their sleep monitored to determine if they had sleep apnea.

They found that 105 women had sleep apnea, also known as sleep-disordered breathing, which caused them to have 15 or more events an hour while they slept. Of those women 44.8 percent developed mild cognitive impairment or dementia after five years, compared with 31 percent of 193 women without sleep apnea.

The results showed that women with sleep apnea had a 1.8 times higher risk for developing mild cognitive impairment or dementia. When the data was adjusted to include baseline cognitive test scores, the results showed a 2.36 times higher risk, the researchers said.

It's unknown at what age sleep apnea has to start to raise dementia risk, Stone said. Sleep apnea affects up to 10 million Americans, according to the American Association of Respiratory Care.

"We've known for some time that there is a link between sleep disordered breathing and brain function, but ours is the first study to demonstrate that SDB in cognitively normal older adults is a risk factor for the development of poor cognition over time," said lead study author Kristine Yaffe, a professor of psychiatry, neurology and epidemiology at the University of California, San Francisco, in a statement. "More studies are needed in which older adults with SDB are treated to determine if the decline in mental function can be slowed or prevented."

Treatments for sleep apnea include surgery or continuous positive air pressure, where a machine provides air to the airways through a mask or nasal prongs preventing the airways from collapsing and causing breathing to stop during sleep, Stone said.

Luigi Ferini-Strambi, an associate professor and director of the Sleep Disorders Center at University Vita-Salute San Raffaele in Milan, wrote in an accompanying editorial with colleague Nicola Canessa that studies for treatments of cognitive function in patients with mild cognitive impairment or dementia should also consider whether sleep apnea is present.

"No medications are known to prevent the development of dementia," said Ferini-Strambi in an Aug. 8 email. "This study suggests that treatment of obstructive sleep apnea in the elderly may be a prevention strategy for mild cognitive impairment and dementia. Obstructive sleep apnea should be considered a possible risk factor for mild cognitive impairment and dementia."

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