A study published in the Journal of the American Medical Association supported this conclusion. Kristine Yaffe, a professor of psychiatry at the University of California-San Francisco, led a study that recruited nearly 300 elderly women who were mentally and physically fit. The average age of the subjects in the study was 82. Each woman spent a night in a sleep lab, and Yaffe found that about 1 in every 3 met the standard for sleep apnea. Yaffe re-examined each woman five years later. The effects of age on the mind seemed to depend on the quality of sleep. Nearly half of the women with sleep apnea showed signs of mild cognitive impairment or dementia, compared with only a third of the women who slept normally. After controlling for factors such as age, race, and the use of medicines, Yaffe found that the women with sleep apnea were 85 percent more likely to show the first signs of memory loss. The frequent interruptions in sleep and the reduced oxygen in the brain may reduce the brain’s ability to form and protect long-term memories.