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Sleep-Disordered Breathing is a Risk Factor for Dementia
Abstract & Commentary
By Michael Lin, MD, Associate Professor of Neurology and Neurosciences, Weill Cornell Medical College. Dr. Lin reports no financial relationships relevant to this field of study.
Synopsis: Sleep-disordered breathing is a significant risk factor for cognitive decline and continuous positive airway pressure (CPAP) therapy may prevent or slow this process.
Source: Yaffe K, et al. Sleep-disordered breathing, hypoxia, and risk of mild cognitive impairment and dementia in older women. JAMA 2011;306:613-619.
Sleep-disordered breathing affects up to 60% of older adults. It is associated with adverse health outcomes, including hypertension and diabetes. In their recent article, Yaffe and colleagues now report the first longitudinal association of sleep-disordered breathing with later development of mild cognitive impairment (MCI) or dementia.
A sample of 298 older women without dementia, participating in a study of osteoporotic fractures, had baseline cognitive testing and underwent overnight in-home polysomnography. More than one-third had sleep-disordered breathing, defined by an apnea-hypopnea index > 15 events/hour, but those with and without sleep-disordered breathing did not differ at baseline. Cognition was reassessed approximately 5 years later, and 44.8% of subjects with sleep-disordered breathing developed MCI or dementia compared with 31.1% of subjects without sleep-disordered breathing. When adjusted for age, race, education, BMI, smoking, diabetes, hypertension, use of antidepressants, benzodiazepines, or other anxiolytics, and baseline cognitive scores, the odds ratio was 2.36 (95% confidence interval 1.34-4.13). The authors also examined which effects of sleep-disordered breathing were most critical in mediating the risk for MCI or dementia. Measures of hypoxia were associated with increased incidence of MCI or dementia, but measures of sleep fragmentation or duration were not. This is consistent with the known sensitivity of the hippocampus to hypoxia, and the importance of the hippocampus in MCI and dementia.
This work has implications for prevention and treatment of dementia. Sleep-disordered breathing and cognitive deterioration are both extremely common in aging, and even a modest effect of (CPAP) therapy or possibly oxygen supplementation in decreasing the risk for MCI and dementia could have a large impact. In subjects who already have Alzheimer's disease, trials of CPAP for sleep-disordered breathing have shown slowed deterioration or even improvement in cognition. Thus, sleep-disordered breathing should be considered in all patients with MCI or dementia, and treatment initiated if appropriate.