Obstructive sleep apnea and other sleep disorders have long been associated with cognitive dysfunction, but so far not in a prospective study. So, Yaffe et al followed 298 older women (~82 years) who had already had polysomnography as part of an osteoporosis study.
105 had sleep disordered breathing (cases), defined as an apnea-hypopnea index >= 15, while 193 did not (controls). Compared to controls, older women with obstructive sleep apnea or other SDB were more likely to develop cognitive dysfunction during the study period (a raw rate of 45% vs 31%). After multivariate regression to control for age, comorbid illness like diabetes, hypertension, medications use, etc., sleep-disordered breathing remained an independent predictor of the future onset of cognitive dysfunction, with an odds ratio of 1.85. JAMA 2011;306:613-619.