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AASM hypopnea definition best for detecting OSA cases, study finds



– The prevalence of obstructive sleep apnea (OSA) is substantially lower using the Centers for Medicare & Medicaid Services apnea-hypopnea index definition of OSA than using the one recommended by the American Academy of Sleep Medicine.

Dr. Stuart F. Quan Brigham and Women's Hospital Division of Sleep and Circadian Disorders, Boston. Doug Brunk/MDedge News

Dr. Stuart F. Quan

In addition, among individuals who did not have OSA using the CMS definition but met criteria using the AASM definition of OSA, an apnea-hypopnea index (AHI) of five events or greater per hour was associated with a greater likelihood of having hypertension.

The findings come from an analysis which set out to assess the relationship between OSA and hypertension using the AASM-recommended definition and the 2018 American Heart Association/American College of Cardiology blood pressure guidelines, and to determine if there is an association between hypertension and OSA among individuals who did not meet the CMS definition of OSA.

“Given the substantial morbidity associated with hypertension, these results suggest that universal adoption of the AASM AHI definition would be a reasonable step in ensuring appropriate diagnosis and treatment of OSA,” lead study author Stuart F. Quan, MD, said at the annual meeting of the Associated Professional Sleep Societies.

Dr. Quan, of the division of sleep and circadian disorders at Brigham and Women’s Hospital in Boston, noted that a number of studies have demonstrated that OSA is a risk factor for hypertension and a variety of other medical conditions. “Rightly or wrongly, the most important metric for determining whether OSA is present and determining its severity, is the apnea-hypopnea index,” he said. “It’s the most common metric used for determining OSA severity, and mostly importantly, Medicare and some other insurers use this metric to determine whether a person is eligible for treatment. If a person falls above the line, they can get continuous positive airway pressure, for example. If they’re below the line, that’s too bad; they don’t have OSA insofar as the insurance company is concerned.”

There is no controversy as to what constitutes apnea, he continued, but some disagreement exists on the definition of hypopnea. The AASM recommends using a 3% oxygen desaturation or an arousal, while Medicare uses a definition of hypopnea requiring only a 4% oxygen desaturation. Hypertension definitions have changed recently as well. Before 2018, the definition of hypertension was greater than 140/90 mm Hg for people younger than age 65 years and 150/80 mm Hg for people age 65 years and older. In 2018, the AHA and ACC changed the hypertension guidelines, defining normal as less than 120/80 mm Hg.

“Previous studies linking OSA and hypertension used older definitions, but to my knowledge there are no current studies examining the association between OSA and hypertension using new definitions,” Dr. Quan said.

He reported on results from an analysis of 6,307 participants in the Sleep Heart Health Study who underwent home polysomnography. Their AHI defined by a 3% oxygen desaturation or an arousal was classified into four categories of OSA severity: fewer than 5 events per hour (normal sleep), 5-14 events per hour (mild sleep apnea), 15-29 events per hour (moderate sleep apnea), and 30 or more events per hour (severe sleep apnea).

The researchers used three definitions of dichotomous BP elevation: elevated (greater than 120/80 mm Hg or use of hypertension medications [meds]), stage 1 (greater than 130/80 mm Hg or meds), or stage 2 (greater than 140/90 mm Hg or meds). They used logistic regression to assess the association between elevated BP and/or hypertension and OSA severity, controlling for demographics and body mass index. Additional analyses utilized multiple linear regression to determine the relationship between natural log AHI and systolic and diastolic BP, controlling for the same covariates.

For all definitions of elevated BP, increasing OSA severity was associated with greater likelihood of an elevated or hypertensive status in fully adjusted models. Specifically, the odds ratios among those with elevated BP was 1.30 (95% confidence interval, 1.10-1.54), 1.41 (95% CI, 1.15-1.72), and 1.69 (95% CI, 1.32-2.17) for mild, moderate, and severe sleep apnea, respectively. The ORs among those with stage 1 BP was 1.27 (95% CI, 1.09-1.49), 1.36 (95% CI, 1.13-1.63), 1.58 (95% CI, 1.27-1.97) for mild, moderate, and severe sleep apnea, while the OR among those with stage 2 BP was 1.07 (95% CI, 0.92-1.26), 1.22 (95% CI, 1.02-1.45), 1.38 (95% CI, 1.12-1.69) for mild, moderate, and severe sleep apnea. Linear regression found that AHI was associated with both systolic and diastolic BP in fully adjusted models.

“Using the AASM and CMS AHI definitions, increasing severity of AHI is associated with greater likelihood of having an elevated blood pressure or hypertension,” Dr. Quan concluded. “However, the prevalence of OSA was substantially lower using the CMS definition of OSA. In fact, 218 of these individuals had moderate to severe OSA when the AASM definition was applied.”

He characterized the study as “a practical analysis, a way to help identify patients who might benefit from treatment. This is not the issue of whether the science of 3% AHI is better than 4%.”

The Sleep Heart Health Study was supported by the National Heart, Lung, and Blood Institute. Dr. Quan reported that he helped draft the AASM AHI recommendations but had no other relevant disclosures.

SOURCE: Quan SF et al. SLEEP 2019, Abstract 0501.

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