Better Sleep Metrics Can Identify CVD Risk in Sleep Apnea

MIAMI—Obstructive sleep apnea (OSA) is known to increase the risk of early mortality, stroke, and cardiovascular disease (CVD).

A study published in the journal Frontiers in Neurology noted that OSA is defined by the apnea–hypopnea index, a severity index that combines apneas (pauses in breathing) and hypopneas (partial obstructions in breathing) associated with hypoxemia. The authors from the Miami VAMC and the University of Miami suggested, however that other sleep metrics such as oxygen nadir and arousal frequency, along with clinical symptoms and molecular markers could be better predictors of stroke and CVD outcomes in OSA.1

“The recent focus on personalized medical care introduces the possibility of a unique approach to the treatment of OSA based on its phenotypes, defined by pathophysiological mechanisms and/or clinical presentation,” they wrote.

The researchers performed a systematic review from Jan. 1, 2007, to Nov. 1, 2017, by searching the PubMed and Embase databases, looking for  the terms “obstructive sleep apnea” or “sleep disordered breathing” and “phenotype” or “phenotypes.” Also articles were searched with the key word “obstructive sleep apnea phenotypes.” The first author also evaluated the abstract for articles that included “cardiovascular disease,” or “stroke,” or “cerebrovascular disease.” The 14 articles meeting inclusion criteria were independently reviewed for additional information by the authors.

Results indicate that most of the articles used clinical symptoms to define OSA phenotypes, followed by experimental or data-driven approach and by molecular-genetic studies.

The authors said they found it interesting that studies using empirically or data-driven analytical methods such as cluster analysis, observed increased cardiovascular outcomes in patients without daytime sleepiness. Instead, those patients who were defined as having “poor,” “fragmented” sleep predominantly with insomnia symptoms or periodic limb movements had increased cardiovascular outcomes.

“In our systematic review, most studies sampled middle-aged males from sleep centers. Of importance, studies derived solely from sleep centers are of limited external validity and generalizability due to possible selection bias,” the researchers wrote. “Consequently, there is a need to develop tools for health-care professionals, sleep specialist, and scientist to further recognize and risk-stratify different OSA phenotypes; particularly in older-adults and females. Importantly, population-based studies can help further evaluate age, sex and ethnic differences in OSA phenotypes; allowing clinicians and researchers to recognize participants an increased risk of stroke and CVD ,especially in populations with large burden of CVD that may benefit from inclusion in treatment studies.”

1. Ramos AR, Figueredo P, Shafazand S, Chediak AD, et. cal. Obstructive Sleep Apnea Phenotypes and Markers of Vascular Disease: A Review. ,Front. Neurol., 05 December 2017 https://doi.org/10.3389/fneur.2017.00659.

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