Sleep disordered breathing is a spectrum of sleep related breathing abnormalities that includes obstructive sleep apnea, central sleep apnea, and mixed or complex sleep apnea. These disorders are characterized by abnormally long pauses in breathing during sleep, which is referred to as apnea. Abnormally low breathing events also occur and they are referred to as hypopnea. These disorders are diagnosed with an overnight polysomnogram, which is commonly referred to as a “sleep study”. The most common symptom of obstructive sleep apnea is snoring, which results when a physical obstruction to airflow occurs despite adequate respiratory drive. In central sleep apnea, the respiratory drive is dysfunctional. Complex or mixed sleep apnea results when there is a combination of both airflow obstruction and dysfunctional respiratory drive. Sleep disordered breathing has been associated with the development of other medical disorders including hypertension, heart disease, and diabetes. Cognitive impairment has also been associated with sleep disordered breathing, but whether the sleep disorder precedes the impairment of cognition has been unclear. Researchers lead by Dr. Kristine Yaffe have found that in older women, sleep disordered breathing is associated with increased risk of developing mild cognitive impairment and dementia. The results of their research were published online in the Journal of the American Medical Association. The researchers used a prospective sleep and cognition study that included 298 women without baseline dementia. These women were part of a substudy of the Study of Osteoporotic Fractures. The women had a mean age of 82 and all had overnight polysomnography performed at the start of the study. 35% of the women (105 women) were diagnosed with sleep disordered breathing at the start of the study, and the women were followed for a median of 4.7 years. During the follow up period, the women with sleep disordered breathing were more likely to develop mild cognitive impairment or dementia (44% of the women) compared to women who did not have sleep disordered breathing (31% of the women). Hypoxia was associated with the development of mild cognitive impairment and dementia, while sleep fragmentation and sleep duration were not associated. The authors hypothesize that hypoxia may be the mechanism whereby sleep disordered breathing leads to mild cognitive impairment or dementia. The authors wrote, “We found that among women with a mean age of 82 years, sleep disordered breathing was associated with an increased risk of cognitive impairment. Our results indicate that this relationship seems to be related primarily to measures of hypoxia. Given the high prevalence of both sleep disordered breathing and cognitive impairment among older adults, the possibility of an association between the 2 conditions, even a modest one, has the potential for a large public health impact. Furthermore, the finding that hypoxia and not sleep fragmentation or duration seems to be associated with risk of mild cognitive impairment or dementia provides clues to the mechanisms through which sleep-disordered breathing might promote cognitive impairment”. Future studies will focus on whether oxygen supplementation and treatment of sleep disordered breathing can slow the progression of mild cognitive impairment to dementia.
See the YouTube video interview with Dr. Katie Stone below:
Kristine Yaffe et al. “Sleep-Disordered Breathing, Hypoxia, and Risk of Mild Cognitive Impairment and Dementia in Older Women” JAMA 2011;306(6):613-619. doi: 10.1001/jama.2011.1115