Sleep Apnea Tied to Worse Cognition

By Todd Neale, Senior Staff Writer, MedPage Today Published: August 09, 2011 Reviewed by Zalman S. Agus, MD; Emeritus Professor University of Pennsylvania School of Medicine.

Older women with sleep-disordered breathing are more likely to develop cognitive impairment than those who don't have sleep problems, researchers found. Through nearly five years of follow-up, women 65 and older who had sleep-disordered breathing at baseline had a higher rate of incident mild cognitive impairment or dementia (44.8% versus 31.1%, P=0.02), according to Kristine Yaffe, MD, of the University of California San Francisco, and colleagues. After adjustment for numerous potential confounders, including baseline cognition, women with sleep-disordered breathing maintained a higher likelihood of cognitive impairment (OR 2.36, 95% CI 1.34 to 4.13), the researchers reported in the Aug. 10 issue of the Journal of the American Medical Association. "Given the high prevalence of both sleep-disordered breathing and cognitive impairment among older adults, the possibility of an association between the two conditions, even a modest one, has the potential for a large public health impact," they wrote. These findings and those from related studies, according to Nicola Canessa, PhD, and Luigi Ferini-Strambi, MD, of Vita-Salute San Raffaele University in Milan, "suggest that large trials with continuous positive airway pressure treatment in elderly participants with sleep-disordered breathing should be performed." "Moreover," they wrote in an accompanying editorial, "in trials evaluating the effects of pharmacological and nonpharmacological ... interventions on cognitive function in patients with mild cognitive impairment or dementia, the possible coexistence of sleep-disordered breathing should be considered." Although previous studies have linked sleep-disordered breathing with poor cognition, it had remained unclear whether the sleep problem preceded cognitive decline in older adults, according to the researchers. To explore the issue, they evaluated data on 298 older women (mean age 82) who were free of dementia at baseline and who participated in the sleep and cognition substudy of the Study of Osteoporotic Fractures. All underwent overnight polysomnography in their homes for one night at baseline, which revealed that about one-third (35.2%) had sleep-disordered breathing, defined as 15 or more apnea or hypopnea events per hour of sleep. Through a median follow-up of 4.7 years, 20.1% of the participants developed mild cognitive impairment and 15.8% developed dementia. Women who had sleep-disordered breathing were significantly more likely to develop cognitive impairment during follow-up, after adjustment for age, race, body mass index, education, smoking status, diabetes, hypertension, medication use, and baseline cognition. Although sleep fragmentation and duration were not related to the odds of developing cognitive impairment, two measures of hypoxia -- an elevated oxygen desaturation index and a high percentage of sleep time in apnea or hypopnea -- were associated (ORs 1.98 and 2.32, respectively). "This suggests that hypoxia is a likely mechanism for this relationship, which is supported by recent animal models of chronic hypoxia that demonstrated similar impairments in cognition with possible implications for apolipoprotein E, inflammatory, and regulatory pathways," Yaffe and colleagues wrote. "However," they added, "it is important to note that because cerebral blood flow may be affected in elderly patients, other mechanisms such as hypercapnia could also be involved." They acknowledged that some misclassification of sleep-disordered breathing status was possible because polysomnography was performed on only one night. The study was also limited by the inclusion of mostly white women, which limits the generalizability to other populations, and possible survival bias. The Study of Osteoporotic Fractures is supported by the National Institutes of Health (NIH). The National Institute on Aging (NIA) provided support for the current study. Yaffe is supported in part by a grant from the NIA. One of her co-authors is supported by a Mentored Research Scientist Development Award from the NIA. Another study author is supported by an NIA grant. Yaffe reported links with Novartis, Pfizer, Medivation, the National Institute of Mental Health, Beeson Scientific Advisory, NIH, the Alzheimer's Association, the Department of Defense, the American Health Assistance Foundation, Japan Geriatrics Society, Wake Forest University, and the State of California Department of Human Services. Her co-authors reported relationships with the NIH, the American Academy of Sleep Medicine, Johnson & Johnson, Merck, Purdue Pharma LP, sanofi-aventis, and Pfizer. Ferini-Strambi reported that he is a board member for Boehringer Ingelheim, UCB-Pharma, GlaxoSmithKline, and sanofi-aventis.

Primary source: Journal of the American Medical Association Source reference: Yaffe K, et al "Sleep-disordered breathing, hypoxia, and risk of mild cognitive impairment and dementia in older women" JAMA 2011; 306: 613-619. Additional source: Journal of the American Medical Association Source reference: Canessa N, Ferini-Strambi L "Sleep-disordered breathing and cognitive decline in older adults" JAMA 2011; 306: 654-655.