Sleep-Disordered Breathing Raises Risk for Cognitive Decline

Megan Brooks

August 29, 2017

Sleep-disordered breathing (SDB) is associated with an increased risk for cognitive impairment and a worsening of executive function, suggests a new systematic review and meta-analysis of more than 4 million adults. 

"Clinicians should pay more attention to their patients' sleep problems, such as sleep apnea. It is important for clinicians to make sure that a patient’s SDB is diagnosed and treated promptly," Yue Leng, PhD, Department of Psychiatry, University of California, San Francisco, told Medscape Medical News.

Dr Yue Leng

A growing number of studies have suggested a potential link between SDB and cognitive decline in the elderly, but results have been conflicting and studies have used different designs and methods, making it difficult to draw conclusion on the consistency of the association, said Dr Leng.

"The current study is the first to quantitatively synthesize all published population-based studies on SDB and cognitive function and to conclude on the effects of SDB on both the risk of cognitive impairment and on different domains of cognitive function," she said.

The findings were published online August 28 in JAMA Neurology.

Key Modifiable Risk Factor

The researchers did a systematic search of PubMed, EMBASE, and PsychINFO to identify peer-reviewed articles published in English before January 2017 that reported on the association between SDB and cognitive function. The analysis included 14 studies, of which 6 were prospective. Each had at least 200 participants, for a total population of 4.2 million men and women (mean age, 40 years or older).

Pooled analysis of the prospective studies showed that individuals with SDB were 26% more likely to develop cognitive impairment (risk ratio, 1.26; 95% confidence interval [CI], 1.05 - 1.50). No evidence of publication bias was found, but there was significant heterogeneity between studies.  After elimination of one study that introduced significant heterogeneity, the pooled risk ratio was 1.35 (95% CI, 1.11 - 1.65).

Pooled analysis of the cross-sectional studies suggested that patients with SDB had slightly worse executive function (standard mean difference, –0.05; 95% CI, –0.09 to 0.00), with no evidence of heterogeneity or publication bias. SDB was not associated with global cognition or memory.

"Our findings provide evidence that SBD may be an important modifiable risk factor for cognitive impairment in elderly persons," the investigators write.

"Clinicians should closely follow patients who experience significant levels of SDB for the occurrence of cognitive dysfunction and might consider administering full neuropsychological batteries in some instances," said Dr Leng. "This is potentially important for the early detection of dementia."

Future studies, she added, need to examine whether treatment of SDB could help improve cognition and reduce the risk for dementia, which "might open up new opportunities for the prevention and management of dementia in the elderly."

Cause for Concern

Commenting for Medscape Medical News, Lawrence Epstein, MD, medical director of clinical sleep medicine at Brigham and Women's Hospital in Boston, Massachusetts, said that the findings in this meta-analysis are important.

"Sleep apnea has always been known to cause impacts on how people feel and how they think, and lots of studies over time have suggested permanent changes in different types of cognitive function. But the studies tended to be small so the generalizability was limited," said Dr Epstein.

"The advantage of a study like this is that in pooling all the data you get up to over 4 million people, and it's much easier to see the impact — and in a more robust way and in a way that is more believable."

The results suggest that there is a "need to be concerned; that the risk of long-term cognitive dysfunction is about 26% higher in people with sleep apnea than in those without and that's a pretty large amount," added Dr Epstein, who is also past president of the American Academy of Sleep Medicine and president and CEO of Welltrinsic Sleep Network.

SDB is a "very treatable, very common disorder that has significant impacts on health and optimal functioning. There is not a general awareness of sleep apnea and its negative consequences, and people really tend to underestimate how they are affected by sleep deprivation and sleep problems," he concluded.

The study had no commercial funding. The investigators and Dr Epstein have disclosed no relevant financial relationships.

JAMA Neurol. Published online August 28, 2017. Abstract

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