Harvard Women's Health Watch

Sleep apnea increases dementia risk in older women

More than half of adults ages 65 and over have sleep apnea, a disorder characterized by abnormal pauses in breathing during sleep. Chronic sleep apnea is associated with many health risks, including high blood pressure, heart disease, and stroke. It's also been linked to deficiencies in memory and attention in children and middle-aged adults, but studies of older adults have produced conflicting results. Now, a well-designed study has concluded that older women with sleep apnea are more likely to develop cognitive problems and dementia. The findings were published in The Journal of the American Medical Association (Aug. 10, 2011).

The study. At the start of the study, 298 healthy women, average age 82, completed tests of cognitive function and underwent overnight sleep testing that monitored changes in respiration, heart rate, blood oxygen levels, brain activity, and other measures. Sleep apnea was defined as 15 or more "sleep-disordered breathing events" — pauses in breathing or shallow breathing — per hour. Five years later, the women were given further cognitive tests.

The results. Of the 298 participants, 105 met the criteria for sleep apnea. After five years, 45% of these women had developed mild cognitive impairment or dementia, compared with 31% of those who didn't have sleep apnea. After correcting for various factors including weight, smoking, and medication use, researchers estimated that women with sleep apnea were 85% more likely to have cognitive difficulties after five years than those without sleep apnea. These problems were associated only with the lack of steady oxygen to the brain — not with the number of times a woman woke during the night or her total sleep time.

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