Sleep apnea tied to later dementia

Breathing irregularities that rob the brain of oxygen during sleep may imperil a person’s ability to think straight. A study of women 65 and older finds that those with seriously disordered breathing have an increased risk of developing mild cognitive impairment or dementia in subsequent years, researchers report in the Aug. 10 Journal of the American Medical Association.

Individuals with disordered breathing slow down or stop taking breaths  during sleep and often must gasp to catch up. The condition includes sleep apnea, an abnormal pattern that deprives the brain of oxygen and intermittently interrupts the deep sleep needed for satisfying rest.

Earlier, short-term studies linked disordered breathing to cognitive impairment, citing hypoxia, a lack of oxygen, as a culprit. But long-term data have been lacking.

In the new study, physician Kristine Yaffe of the University of California, San Francisco, and her colleagues tested 298 women, average age 82, from 2002 to 2004 for sleep problems, monitoring each individual overnight and noting any stoppages of air flow in their breathing as well as arousals from sleep. About one-third of the patients had disordered breathing. None of these women was cognitively impaired at the time of the sleep test. After the test, patients were given their scores and told if they showed signs of severe sleep problems, says study coauthor Katie Stone, an epidemiologist at the California Pacific Medical Center in San Francisco. Whether they sought treatment is unknown, she says.

When researchers repeated standard cognition tests on the women roughly five years later, 45 percent of those who had disordered breathing had developed dementia or milder cognitive impairments, compared with 31 percent of those with no breathing irregularities.

In particular, women who had 15 or more breathing stoppages per hour and who spent more than 7 percent of sleep time not breathing during the earlier part of the study were nearly twice as likely as those without breathing problems to develop dementia or other cognitive impairments. Such problems can include forgetfulness, confusion and reasoning problems.

“Clearly, hypoxia isn’t good for the brain,” says Brian Murray, a neurologist at Sunnybrook Health Sciences Centre and the University of Toronto, who wasn’t involved in the study. “This is a huge problem, and it does have very significant public health implications.”

Mark Aloia, a psychologist at National Jewish Health in Denver, agrees. “This definitely strengthens the idea that hypoxia has detrimental effects,” says Aloia, who also is director of clinical research at Respironics, Inc., a manufacturer of electronic breathing devices called continuous positive airway pressure, or CPAP, machines. Patients with obstructive sleep apnea, the most common form of disordered breathing, can benefit from CPAP machines, in which a mask fitted over the mouth and nose delivers air constantly during sleep.

Since no medications are known to prevent mild cognitive impairment from progressing to dementia or Alzheimer’s disease, “treating at-risk patients with CPAP for sleep-disordered breathing is a prevention strategy that may be worth testing,” say Nicola Canessa and Luigi Ferini-Strambi of the San Raffaele Scientific Institute in Milan, writing in the same Journal of the American Medical Association.