Hypoxic Burden Could Be Better Gauge of CVD Risk in Sleep Apnea

NEW YORK (Reuters Health) – Hypoxic burden is a better predictor of cardiovascular disease (CVD) mortality in sleep apnea patients than apnea-hypopnea index (AHI), a new analysis of two large cohort studies suggests.

Nearly half of the patients who were classified as having sleep apnea based on AHI were not at increased risk of dying from heart disease over about a decade of follow-up, Dr. Ali Azarbarzin of Brigham and Women’s Hospital and Harvard Medical School in Boston and colleagues report in the European Heart Journal, online October 30.

 

NEW YORK (Reuters Health) – Hypoxic burden is a better predictor of cardiovascular disease (CVD) mortality in sleep apnea patients than apnea-hypopnea index (AHI), a new analysis of two large cohort studies suggests.

Nearly half of the patients who were classified as having sleep apnea based on AHI were not at increased risk of dying from heart disease over about a decade of follow-up, Dr. Ali Azarbarzin of Brigham and Women’s Hospital and Harvard Medical School in Boston and colleagues report in the European Heart Journal, online October 30.

 

AHI measures the number of times a person wakes up during the night, but cannot indicate the depth and duration of sleep apnea-specific hypoxia. Hypoxic burden is based on the respiratory event-associated area under the desaturation curve from pre-event baseline, a single signal that can be derived from an overnight sleep study.

Dr. Azarbarzin and his team looked at Outcomes of Sleep Disorders in Older Men (MrOS) study, with 2,743 participants, and the Sleep Heart Health Study (SHHS) in 5,111 adults 40 and older, including 53% women.

 

AHI was not associated with the risk of CVD mortality in either study. In MrOS, study participants in the fourth and fifth quintiles based on hypoxic burden had hazard ratios of 1.60 (95% confidence interval, 1.13 to 2.28) and 2.04 (95% CI, 1.34 to 3.09), respectively, for dying of CVD during follow-up compared to those in the first quintile.

In SHHS, those in the top quintile based on hypoxic burden had a mortality hazard ratio of 1.96 (95% CI, 1.11 to 3.43) compared with those in the bottom quintile.

“Maybe this is a better way of measuring sleep apnea burden,” Dr. Azarbarzin told Reuters Health by phone. “There’s a lot more research that has to go into proving that.”

“This was the first significant finding to see if this did a better job of predicting a very important outcome like cardiovascular mortality. Maybe later we can see if it’s associated with sleepiness or traffic accidents or other sequelae of sleep apnea,” he added.

“If this turns out to be an important measure of sleep apnea burden then it does have the advantage of being easier to detect and measure than the AHI,” Dr. Andrew Wellman, also at Brigham and Women’s and the study’s senior author, told Reuters Health by phone. “Whether the AHI is measured in the laboratory or at home, it still requires a lot of different signals.”

Hypoxic burden is based on a single signal that can be measured with a pulse oximeter.

The findings come during a time of crisis in the field, after large randomized controlled trials found no effect of sleep-apnea treatment on CVD mortality, leaving clinicians unsure what to do with these patients, Dr. Wellman said. Results of these studies could have been null because they used AHI to classify patients’ risk, he added.

Both authors consult for Somnifix, a company that makes devices to prevent snoring. Dr. Wellman also has a financial interest in Apnimed Corp., which is developing pharmacologic therapies for sleep apnea, and consults for several other companies.

 

SOURCE: https://bit.ly/2B5iN6Z

 

Eur Heart J 2018.

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