Beyond AHI

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How dentists can holistically assess obstructive sleep apnea patients 

Obstructive sleep apnea poses a whole-body threat to patients’ quality and longevity of life. Interrupted sleep and repetitive loss of oxygen can severely impact OSA patients’ long-term health, as they experience hundreds to thousands of apnea or hypopneas over the progression of this condition. Having OSA means patients have a higher risk of numerous life-threatening chronic conditions, including cardiovascular disease, hypertension, cancer, dementia, and Type 2 diabetes.1

Dentists and dental sleep specialists often rely on the Apnea-hypopnea index (AHI) to assess patients’ OSA severity and progression. Increasingly, clinical case studies and research into sleep medicine are bringing into question how effective maintaining this decades-old diagnostic practice is for patients’ health outcomes.

Is AHI always a reliable measure of OSA severity?

AHI measures how often a patient experiences obstructive or mixed apnea or hypopneas, expressed as a rate of discrete apnea/hypopnea incidences per hour. For decades, sleep medicine researchers and healthcare providers working in sleep medicine have used this metric to establish cutoffs to the segment OSA population by severity:1,2

  • No diagnosis: Less than 5 AHI
  • Mild OSA: 5 to 15 AHI: Mild OSA
  • Moderate OSA: 15 to 30 AHI: M
  • Severe OSA: 30 AHI

For decades, researchers, dentists, and sleep medicine specialists have used these cutoffs as a way to consistently assess patients’ severity and progression of OSA. 

But some researchers have found the consistency and reliability of this index questionable, particularly because different entities–including the American Academy of Sleep Medicine (AASM) and the Centers for Medicare and Medicaid Services(CMMS)–have different understandings of AHI.2 

AASM and CMMS each use one of the two common definitions of AHI that use different criteria to determine when interrupted breathing during sleep constitutes hypopnea. The AASM follows the definition that states hypopneas occur when “either an electroencephalogram arousal or ≥ 3% oxygen desaturation” are detected(3%ODA), whereas the CMMS’s preferred definition upholds a less inclusive standard, requiring more than 4% oxygen desaturation to consider interrupted breathing a hypopnea.2

Based on a meta-analysis of over 30 studies, having two different AHI definitions in use in the field of sleep medicine can result in real-world consequences for patient outcomes. The analysis found that 17% of study participants would qualify for an OSA diagnosis under the 3%ODA criteria but not if the 4%OD definition was used. These findings, among others, call into question whether health care providers like dentists and dental sleep specialists should rely on AHI alone to assess patients showing signs of OSA.

How can dentists and dental sleep specialists assess OSA patients beyond AHI?

IN addition to inconsistent definitions of AHI, the index alone can correlate poorly with other measures of OSA severity, which is why dentists and dental sleep specialists need other ways to assess OSA patients. Research has shown that measures of excessive daytime sleepiness–one of the most debilitating day-to-day symptoms of OSA–often do not correlate with OSA severity metrics that are solely based on AHI.3

According to Dr. Steve Lamberg, health care providers treating OSA patients should adopt a more holistic approach to screening and staging OSA, rather than relying on AHI alone to determine disease progression and severity.4 

Instead of focusing on the rate of “scored” apneas and hypopneas that patients experience during sleep, Dr. Lamberg recommends that health care providers focus on the combination of disease process and activity level by staging and grading sleep-related breathing disorders (SRBD) like OSA. 

Healthcare providers can categorize patients’ current OSA severity and systemic damage from Stages 1 to 4, measuring tissue damage due to interrupted breathing using:

  • Patients’ medical history
  • Results from the Lamberg Questionnaire v14
  • Physical examinations
  • Laboratory testing

At the same time, providers can assess the risk that a patient’s SRBD will progress, ranging from Grade A (little to no progression) to Grade C (rapid progression) based on a range of systemic inflammatory biomarkers.

Scoring and grading OSA patients enables better long-term care and health outcomes

This approach takes into account the varied rates of sleep interruption as well as how patients suffer different levels of oxygen deprivation, particularly among those that more often experience hypopneas rather than complete apneas.

Taking a scoring and grading approach allows dentists and dental sleep specialists to more holistically assess where patients fall within the broad range of OSA presentations. In the long run, this approach also supports more focused and effective treatments compared to using strict cutoffs based on AHI alone as a diagnostic model. 

Itamar Medical is a global medical device company specializing in sleep apnea diagnosis & management with the WatchPAT home sleep apnea test (HSAT).

References:

  1. American Dental Association. Oral health topics – Sleep apnea (obstructive). https://www.ada.org/en/member-center/oral-health-topics/sleep-apnea-obstructive. Accessed July 22, 2021.
  2. Kapur VK, Donovan LM. Why a single index to measure sleep apnea is not enough. Journal of Clinical Sleep Medicine. 2019;15(5):683–684. https://jcsm.aasm.org/doi/10.5664/jcsm.7746 
  3. Cielo CM, Tapia IE. Diving Deeper: Rethinking AHI as the Primary Measure of OSA Severity. Journal of Clinical Sleep Medicine. 2019;15(8):1075-1076. doi:10.5664/jcsm.7856.
  4. Lamberg, Transcending AHI. Dental Sleep Practice. https://dentalsleeppractice.com/transcending-ahi/. Accessed July 22, 2021