sleep-disordered breathing

A recent systematic review investigated the potential connection between sleep-disordered breathing and cognitive decline and dementia in the elderly.

Sleep-disordered breathing (SDB) such as sleep apnea (a common disorder where you intermittently stop breathing for many seconds to minutes) and snoring, has been increasingly linked to health problems such as diabetes, heart disease, and high blood pressure. While sleep-disordered breathing is widespread, it is also a treatable condition in ageing adults. This may come as a relief to many, as more recent research has drawn a connection between sleep-disordered breathing and cognitive decline.

Though numerous population-based studies have been conducted to further explore this potential link, results have been conflicting, possibly due to the diversity of study designs and methods used to assess sleep-disordered breathing (SDB). Furthermore, many studies measure and report cognitive results differently. Without consistency, it is difficult to come to a concrete conclusion. Luckily, an American research group set out to look at all of these studies together and use statistics to find out more about the link between SDB and cognitive impairment.

The results of this study—the first of its kind, were recently published in JAMA Neurology. The researchers, based at the University of California, systematically searched PubMed, EMBASE, and PsycINFO to identify peer-reviewed articles published in English before January 2017 that explored the link between SDB and cognitive function. Cross-sectional and prospective studies were included if they included at least 200 participants with an average age of 40 years or older. In all, 14 studies involving a total of 4,288,419 men and women were included in the analysis.

The combined analysis of over four million adults showed that those with SDB were 26% more likely to develop cognitive impairment. This cognitive decline involved a decline in executive function (the ability to reason, plan, focus, and solve problems) but not in either overall cognition or memory. While there were some discrepancies between studies, a sensitivity analysis was conducted, ruling out any publication bias and confirming these associations. These findings are important, highlighting a risk factor for cognitive impairment in the elderly that can actually be modified and treated. Researchers think that the daytime sleepiness, sleep disruption, oxidative stress, and low blood oxygen levels related to SDB may be the reason for the observed neurocognitive decline.

Given the widespread nature of both sleep-disordered breathing and cognitive impairment in our ageing population, these results have important clinical implications. While future studies are still required find out whether treatment of sleep-disordered breathing can prevent cognitive impairment, the researchers nonetheless urge medical professionals to follow elderly patients with sleep-disordered breathing more closely as it may allow for earlier detection of dementia.

Written by Rebecca Yu

Reference: Leng, Y., McEvoy, C. T., Allen, I. E., & Yaffe, K. (2017). Association of Sleep-Disordered Breathing With Cognitive Function and Risk of Cognitive Impairment: A Systematic Review Meta-analysis. JAMA Neurology.

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