A study published in the August 10 issue of JAMA revealed, that older women with sleep-disordered breathing, as indicated by measures of hypoxia (oxygen deficiency), were more likely to develop cognitive impairment or dementia than women without this disorder.
According to background information in the article, sleep-disordered breathing, a condition where the person has recurrent arousals from sleep and intermittent hypoxemia, is common among older people, affecting up to 60 percent of the elderly population. The condition has been linked to various adverse health problems including hypertension, cardiovascular disease and diabetes.
Some studies have also associated cognitive impairment to sleep-disordered breathing; however, the design of most of those studies had a limited ability to draw conclusions. The background information in the article states:
“Given the high prevalence and significant morbidity associated with both sleep-disordered breathing and cognitive impairment in older populations, establishing whether a prospective association exists between sleep-disordered breathing and cognition is important. This is especially important because effective treatments for sleep-disordered breathing exist.”
A study led by Kristine Yaffe, M.D., of the University of California, San Francisco, and her fellow researchers investigated the link between prevalent sleep-disordered breathing measured with polysomnography (monitoring of physiological activity during sleep) and the subsequent diagnoses of mild cognitive impairment and dementia.
The study tested 298 women with an average age of 82.3 years without dementia at the start of the study. All women had an overnight polysomnography between January 2002 and April 2004 in a substudy of the Study of Osteoporotic Fractures. The sleep-disordered breathing was specified as an apnea-hypopnea index (number of complete cessations (apnea) and partial obstructions (hypopnea) of breathing occurring per hour of sleep) of 15 or more.
The participants’ cognitive status (normal, dementia, or mild cognitive impairment) was extracted from data accumulated between November 2006 and September 2008. The study examined measures of hypoxia, sleep fragmentation and sleep duration as underlying mechanisms for any link between sleep-disordered breathing and cognitive impairment.
35.2 percent of the 298 women tested met the criteria for sleep-disordered breathing. 35.9 percent of the women developed mild cognitive impairment (20.1 percent) or dementia (15.8 percent) after an average follow up of 4.7 years. The study revealed, 47 of women (44.8 percent) with sleep-disordered breathing acquired mild cognitive impairment or dementia in comparison with 31.1 percent of those without sleep-disordered breathing.
Data evaluation therefore suggests a link between the presence of sleep-disordered breathing to a higher possibility of developing mild cognitive impairment or dementia. Research also revealed that the two measures of hypoxia (an oxygen desaturation index of 15 or greater and a high percentage of total sleep time [greater than 7 percent] in apnea or hypopnea) were linked to higher occurrences of mild cognitive impairment of dementia after various demographic risk factors were adjusted.
The authors added that the association of sleep-disordered breathing with a higher risk of cognitive impairment seems to be mainly related to measure of hypoxia.
They wrote:
“Measures of sleep fragmentation (arousal index and wake after sleep onset) or sleep duration (total sleep time) were not associated with risk of cognitive impairment. 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.
The increased risk for cognitive impairment associated with sleep-disordered breathing opens a new avenue for additional research on the risk for development of mild cognitive impairment or dementia and exploration of preventive strategies that target sleep quality including sleep-disordered breathing.”
The authors point out that additional trials with larger sample sizes, longer treatment periods, and more diverse populations are required in order to fully evaluate the impact of treatment for sleep-disordered breathing in elderly populations.
They concluded:
“Of interest, our findings suggest a potential role for supplemental oxygen therapy for sleep-disordered breathing in elderly individuals; however, its role requires critical evaluation in intervention studies.”
Nicola Canessa, Ph.D., of the Center for Cognitive Neuroscience, and Luigi Ferini-Strambi, M.D., of the Universita Vita-Salute San Raffaele, Milan, Italy, commented:
“The study by Yaffe et al and related studies to date suggest that large trials with continuous positive air pressure (CPAP) treatment in elderly participants with sleep-disordered breathing should be performed” in an accompanying editorial.
Moreover, in trials evaluating the effects of pharmacological and nonpharmacological (e.g., cognitive training and rehabilitation) interventions on cognitive function in patients with mild cognitive impairment or dementia, the possible coexistence of sleep-disordered breathing should be considered. Finally, physicians of patients with mild cognitive impairment and sleep-disordered breathing for whom treatment with CPAP may be indicated should consider these results, and future guidelines to formalize the clinical management of patients with mild cognitive impairment should consider the implications of this study and related research.”