Obstructive sleep apnea (OSA) affects an estimated 30 million Americans.¹ OSA is commonly diagnosed and graded using the apnea-hypopnea index (AHI). In practice, however, the AHI reported for the same sleep study may differ depending on which hypopnea criterion is used during scoring. This is why clinicians, laboratories, and payers may refer to AHI-3 and/or AHI-4 when discussing the same patient’s study results. Differences between these two values can affect diagnostic thresholds, severity classification, and insurance reimbursement guidelines.

What is the Apnea-Hypopnea Index?

The Apnea-Hypopnea Index (AHI) is the average number of apneas (complete cessation of airflow) and hypopneas (partial reduction in airflow) per hour of sleep.² The AHI determines disease severity according to AASM guidelines:

• Normal: AHI < 5 events/hour
• Mild OSA: AHI 5-14 events/hour
• Moderate OSA: AHI 15-29 events/hour
• Severe OSA: AHI ≥ 30 events/hour ²

Importantly, AHI-3 and AHI-4 do not represent two different sleep studies; rather, they are two versions of the apnea-hypopnea index, with the same definition of apnea, differing only in the scoring method for hypopnea.

The Two Hypopnea Scoring Rulesetations

AHI-3

The American Academy of Sleep Medicine (AASM) recommended rule, established in the 2012 scoring manual update, defines a hypopnea as:

A ≥30% reduction in airflow lasting ≥10 seconds, associated with either a ≥3% oxygen desaturation OR an arousal from sleep.²

AHI-4

The AHI-4, AASM acceptable rule, historically aligned with Centers for Medicare & Medicaid Services (CMS) requirements, defines a hypopnea as:

A ≥30% reduction in airflow lasting ≥10 seconds, associated with a ≥4% oxygen desaturation.²

This more stringent criterion focuses on events with clear physiological consequences, specifically significant drops in blood oxygen levels. The rationale behind this threshold centers on capturing events with demonstrable cardiovascular and metabolic implications.³

Clinical Implications of the Two Scoring Methods

The choice between AHI-3 and AHI-4 scoring can dramatically affect diagnostic outcomes, particularly across different age groups. According to Abbasi-Moradi et al. in Sleep Medicine (2024) ,⁴ changing from the 4% criterion to the updated 3% recommended rule increases OSA diagnosis rates by approximately 27.6% to 38.8% across different age groups(Table 1). ⁴ This surge in positive diagnoses is particularly prominent among patients under age 40 with mild OSA symptoms — a finding that underscores the importance of screening younger patients who may exhibit relatively healthier oxygen desaturation patterns than older OSA patients yet demonstrate alarming arousal patterns (Figure. 1).

Table 1: According to F. AbbasiMoradi et al. 2024, Age-stratified percentage change in OSA severity classification after switching from AHI-4 to AHI-3

Delta Difference% in diagnosis from 4%AHI to 3%AHI

Figure 1: According to F. AbbasiMoradi et al. 2024, graphical representation of the increase in diagnosis of subjects under the updated AASM recommendation rule (AHI-3) from AHI-4 criteria:

Derived from table 2, Abbasi-Moradi et al. 2024

Diagnostic Sensitivity

The AHI-3 rule demonstrates higher sensitivity in detecting:

• Sleep apnea in younger patients with shallower oxygen desaturation pattern⁴
• Case report where upper airway resistance causes arousals without significant desaturation⁵
• REM-related sleep apnea, where events may cause arousals without deep desaturations (especially in women and young patients)^6–10

Population-Specific Considerations

As mentioned before, the following populations show particular vulnerability to underdiagnosis when using AHI-4:

• Women: Often present with more arousals, less severe OSA during NREM, and greater respiratory events during REM.^10,11
• Younger adults: May have greater respiratory reserve, limiting desaturation.¹²
• Patients with comorbid COPD: Complex interactions between respiratory conditions,¹³ often resulting in more arousals and difficulty falling asleep.

Practical Challenges and Controversies

Sleep laboratories face practical challenges in navigating these dual standards. Recommended approaches include:

1. Dual reporting: Providing both AHI-3 and AHI-4 values on every case
2. AASM-standard reporting: Using recommended criteria with supplementary data for insurance policy

Future Technological Directions

Emerging technologies may influence future diagnostic paradigms:

• Hypoxic burden calculations: Quantifying total oxygen deficit rather than event counting¹⁴ (Stay tuned for future blog posts where we will dive into why measuring the hypoxic burden is so critical.)
• Multi-night testing: Capturing night-to-night variability in AHI

What Belun Offers?

Belun Ring provides multi-night Level 3 Sleep test, providing both AHI-3 and AHI-4 scoring and also hypoxic burden, providing more comprehensive phenotyping of patients’ sleep disorders and enabling long-term monitoring of treatment effects.

Key Takeaways: Guidelines for Applying AHI-3 vs. AHI-4 Criteria

AHI-3 is recommended for:

• Initial clinical diagnosis: Particularly for highly symptomatic patients presenting with a sub-threshold AHI.
• Atypical presentations: Specifically, younger patients with a low-to-moderate BMI who exhibit marked daytime fatigue despite minimal oxygen desaturation.
• Targeted demographics: Women with suspected REM-predominant OSA.

AHI-4 is recommended for:

• Cardiovascular risk assessment: When the clinical focus requires identifying events with a more evident hypoxic burden.
• Administrative compliance: Fulfilling documentation requirements for Medicare, payer preauthorization, or PAP therapy reimbursement.
• Longitudinal analysis: Facilitating historical comparisons with older sleep studies, prior clinical reports, or legacy databases.

Conclusion

The distinction between AHI-3 and AHI-4 scoring rules represents more than a technical detail—it fundamentally affects which demographic differences in patients receive diagnoses and access to treatment. AHI3 offers greater sensitivity and better reflects the full spectrum of obstructive sleep apnea pathophysiology, AHI4 creates coverage challenges for these subsets of patients, in particular to younger and female patients with less steep oxygen desaturation patterns and more arousals. Until standardization occurs, the sleep medicine community must remain vigilant in ensuring that scoring methodology differences do not create barriers to necessary care for patients with obstructive sleep apnea.

REFERENCE:

1.             Benjafield, A. V. et al. Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis. Lancet Respir. Med. 7, 687–698 (2019).

2.             Berry, R. B. et al. Rules for scoring respiratory events in sleep: update of the 2007 AASM manual for the scoring of sleep and associated events: deliberations of the Sleep Apnea definitions Task Force of the American Academy of Sleep Medicine. J. Clin. Sleep Med. 08, 597–619 (2012).

3.             Punjabi, N. M., Newman, A. B., Young, T. B., Resnick, H. E. & Sanders, M. H. Sleep-disordered breathing and cardiovascular disease: an outcome-based definition of hypopneas. Am. J. Respir. Crit. Care Med. 177, 1150–1155 (2008).

4.             AbbasiMoradi, F., Mogavero, M. P., Palomino, M., Ferri, R. & DelRosso, L. M. Age related disparities in sleep apnea diagnosis using a wearable device: Implications of 4% vs. 3% hypopnea scoring criteria. Sleep Med. 118, 88–92 (2024).

5.             Guilleminault, C., Stoohs, R., Clerk, A., Cetel, M. & Maistros, P. A cause of excessive daytime sleepiness. The upper airway resistance syndrome. Chest 104, 781–787 (1993).

6.             Mokhlesi, B. & Punjabi, N. M. “REM-related” Obstructive Sleep Apnea: An Epiphenomenon or a Clinically Important Entity? Sleep 35, 5–7 (2012).

7.             Resta, O. et al. Gender difference in sleep profile of severely obese patients with obstructive sleep apnea (OSA). Respir. Med. 99, 91–96 (2005).

8.             Koo, B. B., Patel, S. R., Strohl, K. & Hoffstein, V. Rapid eye movement-related sleep-disordered breathing: influence of age and gender. Chest 134, 1156–1161 (2008).

9.             Goh, D. Y., Galster, P. & Marcus, C. L. Sleep architecture and respiratory disturbances in children with obstructive sleep apnea. Am. J. Respir. Crit. Care Med. 162, 682–686 (2000).

10.          O’Connor, C., Thornley, K. S. & Hanly, P. J. Gender Differences in the Polysomnographic Features of Obstructive Sleep Apnea. Am. J. Respir. Crit. Care Med. 161, 1465–1472 (2000).

11.          Ye, L., Pien, G. W. & Weaver, T. E. Gender differences in the clinical manifestation of obstructive sleep apnea. Sleep Med. 10, 1075–1084 (2009).

12.          Heinzer, R. et al. Prevalence of sleep-disordered breathing in the general population: the HypnoLaus study. Lancet Respir. Med. 3, 310–318 (2015).

13.          Owens, R. L. & Malhotra, A. Sleep-disordered breathing and COPD: the overlap syndrome. Respir. Care 55, 1333–1344; discussion 1344-1346 (2010).

14.          Azarbarzin, A. et al. The hypoxic burden of sleep apnoea predicts cardiovascular disease-related mortality: the Osteoporotic Fractures in Men Study and the Sleep Heart Health Study. Eur. Heart J. 40, 1149–1157 (2019).

Publications by Belun :

1) “Belun® Ring Platform: a novel home sleep apnea testing system for assessment of obstructive sleep apnea” (https://jcsm.aasm.org/doi/10.5664/jcsm.8592),

2) “Detection of obstructive sleep apnea using Belun® Sleep Platform wearable with neural network based algorithm and its combined use with STOP-Bang questionnaire” (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0258040),

3) “Belun® Ring (Belun® Sleep System BLS-100): Deep Learning-Facilitated Wearable Enables OSA Detection, Apnea Severity Categorization, and Sleep Stage Classification in Patients Suspected of OSA”  (https://pubmed.ncbi.nlm.nih.gov/37380590/), 

4) “Correlation of Pulse Rate Variability(PRV) and Heart Rate Variability(HRV) Metrics During Sleep in Subjects Suspected of OSA” (https://academic.oup.com/sleep/article/46/Supplement_1/A420/7182347)

5) “The Belun sleep platform to diagnose obstructive sleep apnea in patients with hypertension and high cardiovascular risk” (https://pubmed.ncbi.nlm.nih.gov/37071415/)

6) “Integrating Body Sensor into a Wearable Platform to Enhance the Identification of Central and Mixed Apneas”. (https://academic.oup.com/sleep/article/47/Supplement_1/A222/7654683)

7) “Using a Wearable’s Multi-Night Capability to Mitigate Night-to-Night Variability in a Dental Clinic Cohort”. J Dental Sleep Med. 2026; 13(1). (https://aadsm.org/journal/original_article_1_issue_131.php)

Partnering with Belun :

If you would like to know more about how to adopt Belun’s solution in your organization, please feel free to contact us to schedule a meeting by filling out the form below:

The post AHI-3 vs AHI-4 in Sleep Apnea Diagnosis: Understanding the Scoring Rules first appeared on Belun Technology.

Belun Technology will partner with Nexter Living (SCG’s subsidiary), a healthcare extension from the conglomerate. A new Brand, “DoCare” is created to cater to the elderly market with the concept of “Making Eldercare Affordable and Convenient for Everyone”. ³

Thailand is among the fastest aging countries in the world; of its 67 million population, 12 million Thais are elderly, according to the latest national statistics report from WHO.² Since 2016, Nexter Living has innovated the smart living series to tackle the aging population.

Source : DoCare’s Facebook

According to the Lancet’s report, 36% of the Thai population has AHI (apnoea-hypopnoea index) >= 5, posing new challenges to the country’s healthcare system with its 20% aging population issue. Research shows sleep health is critical for the overall immune system & treatment effectiveness of chronic diseases. Nexter Living partners with Belun® Ring because of its medical accuracy backed up by the US FDA 510(k) clearance. Belun’s CEO, Lydia Leung, shared: “Belun® Ring is a user and environmentally friendly PPG-based wearable with medical accuracy. Belun will offer a superb convenient option that encourages suspected patients to take action and kick start their treatment journey.”

Nexter Living will promote the Belun Sleep Platform to the local hospital, hotels, wellness centers, elderly homes & new property projects promoting preventive care living. Thailand has been a hub for global medical tourism, and the expanding expatriate communities will also be the target.

Solutions from SCG for the elderly Source: SCG’s website

Chronic Disease Management via AI Preventive Healthcare

Belun’s vision is to help people better manage their chronic diseases through artificial intelligence and big data analytics to alleviate medical expenditures due to the aging population. Its solution allows caregivers and patients to follow their treatment effectiveness, select personalized solutions, and enhance treatment compliance. Lydia further shared: “Long-term monitoring using medical-grade wearables can help people to identify abnormalities earlier to achieve preventive healthcare.” 

Partnering with Belun :

Up to now, over a hundred organizations, including HK hospital authority hospitals, medical groups, clinic groups, dentists, and elderly centers selected to use the Belun Sleep System, Belun Ring, and Belun® remoVital monitoring system. Many doctors read our medical journal papers, including 1) “Belun® Ring Platform: a novel home sleep apnea testing system for assessment of obstructive sleep apnea” (https://jcsm.aasm.org/doi/10.5664/jcsm.8592) and 2) “Detection of obstructive sleep apnea using Belun Sleep Platform wearable with neural network based algorithm and its combined use with STOP-Bang questionnaire” (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0258040).

If you would like to know more about how to adopt Belun’s solution in your organization or home use, please feel free to contact us to schedule a meeting by filling out the form below:

References

1. A.V, Benjafield et al, Lancet Respiratory Medicine, 2019; 2. Susanna Ng et al, PLOS One, 2015

2. https://www.who.int/southeastasia/news/feature-stories/detail/thailands-leadership-and-innovation-towards-healthy-ageing#:~:text=Thailand%20is%20among%20the%20fastest,for%2010%25%20of%20the%20population

3. https://www.scg.com/innovation/%E0%B8%9B%E0%B8%A3%E0%B8%B1%E0%B8%9A%E0%B8%95%E0%B8%B1%E0%B8%A7%E0%B8%AD%E0%B8%A2%E0%B9%88%E0%B8%B2%E0%B8%87%E0%B9%84%E0%B8%A3-%E0%B9%83%E0%B8%99%E0%B8%A7%E0%B8%B1%E0%B8%99%E0%B8%97%E0%B8%B5%E0%B9%88/

The post Belun Technology announces Nexter Living as its Official Distributor in Thailand   first appeared on Belun Technology.

Keep people healthy with our preventive healthcare data

Belun’s CEO, Dr. Lydia Leung, shared: “we hope to facilitate home sleep tests for identifying undiagnosed OSA. Research shows sleep health is critical for the overall immune system & treatment effectiveness of chronic diseases.” The company is expanding towards Preventive Healthcare from the original sleep health. The new direction is an insight found from collaborating with worldwide specialists. Since the launch of our 1st generation Belun Ring in 2018, it has been gradually adopted in other research on long-term diseases, including stroke, hypertension, insomnia, dementia, etc.

“Our new company direction results from the co-created insights after collaborating with worldwide researchers. Sleep takes up so much human time, but we know little about it. Our vision is to keep people healthy with our preventive healthcare data.”

Lydia Leung, CEO of Belun Technology

Worldwide obesity epidemic & the aging population

The sedentary lifestyle of people has led to an increasing prevalence of cardiovascular disease, poor sleep patterns, evaluated stress & obesity. OSA is common in patients with high BMI. Therefore, the worldwide obesity epidemic and the aging population demographic will likely contribute to the rising global prevalence of OSA. According to the World Economic Forum, 1 in 3 adults worldwide will suffer from 2 or more chronic conditions, leading to annual healthcare costs with an 80-300% increment². World Health Organization estimates a projected 10 million health workers shortfall by 2030³. Researchers predicted demand for healthcare workers will increase to 80 million by 2030, but supply will only reach 65 million, creating a healthcare worker deficit of 15 million. The anticipated shortage requires some immediate actions, or access to primary healthcare would be at risk. 

PPG-based wearable with medical accuracy

Belun’s CEO, Lydia Leung, shared: “Belun Ring is a user and environmentally friendly PPG-based wearable with medical accuracy. Belun will offer a superb convenient option that may bring disruption to the sleep health market & encourage suspected patients to take action and kick start their treatment journey.” According to AASM⁴, “ubiquitous availability of PPG technology may allow for OSA diagnosis at scale.” There is “an increased interest in new technologies with therapeutic potential.”

Chronic Disease Management via AI Preventive Healthcare

Belun’s vision is to help people better manage their chronic diseases through artificial intelligence and big data analytics to alleviate medical expenditures due to the aging population. Our solution allows caregivers and patients to follow their treatment effectiveness, select personalized solutions, and enhance treatment compliance. Lydia further shared: “Long-term monitoring using medical-grade wearables can help people to identify abnormalities earlier to achieve preventive healthcare.” 

Worldwide partnership for the OSA markets

To cope with the massive market, Belun has teamed up with global partners to customize solutions for local communities in different countries. Some sleep lab groups in the United States will launch the Belun Sleep System to cater to both the OSA & insomnia markets. For the Indian market, Belun will collaborate with renowned neurologists & sleep specialists to tap into the millions of untreated OSA. The two markets have 104 million suspected OSA, according to the Lancet report¹.

Partnering with Belun :

Up to now, over a hundred organizations, including HK hospital authority hospitals, medical groups, clinic groups, dentists, and elderly centers selected to use the Belun Sleep System, Belun Ring, and Belun® remoVital monitoring system. Many doctors read our medical journal papers, including: 

1) “Belun® Ring Platform: a novel home sleep apnea testing system for assessment of obstructive sleep apnea” (https://jcsm.aasm.org/doi/10.5664/jcsm.8592),

2) “Detection of obstructive sleep apnea using Belun Sleep Platform wearable with neural network based algorithm and its combined use with STOP-Bang questionnaire” (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0258040),

3)Belun® Ring (Belun Sleep System BLS-100): Deep Learning-Facilitated Wearable Enables OSA Detection, Apnea Severity Categorization, and Sleep Stage Classification in Patients Suspected of OSA  (https://journals.lww.com/jhypertension/Abstract/2023/06000/The_Belun_sleep_platform_to_diagnose_obstructive.16.aspx), 

4) Correlation of Pulse Rate Variability(PRV) and Heart Rate Variability(HRV) Metrics During Sleep in Subjects Suspected of OSA (Accepted in SLEEP conference 2023, Abstract ID: 954).

If you would like to know more about how to adopt Belun’s solution in your organization or home use, please feel free to contact us to schedule a meeting by filling out the form below:

References

1.A.V, Benjafield et al, Lancet Respiratory Medicine, 2019; 2. Susanna Ng et al, PLOS One, 2015

2. https://www.weforum.org/agenda/2017/12/healthcare-future-multiple-chronic-disease-ncd/

3. https://www.who.int/news/item/02-06-2022-global-strategy-on-human-resources-for-health–workforce-2030

4. https://aasm.org/wp-content/uploads/2022/05/Tech-Committee-Report.pdf

The post FDA-cleared Belun Sleep System may speed up OSA diagnosis for 1 billion population  first appeared on Belun Technology.

We had a fruitful discussion in the one hour sharing session.

To understand more about how Belun’s applications would help clinical psychologists, see our previous story about CBT-I.

Partnering with Belun :

Up to now, over a hundred organizations, including HK hospital authority hospitals, medical groups, clinic groups, dentists, and elderly centers selected to use the Belun Sleep System, Belun® Ring and Sleep App, and Belun® remoVital monitoring system. Many doctors read our medical journal papers, including: 

1) “Belun® Ring Platform: a novel home sleep apnea testing system for assessment of obstructive sleep apnea” (https://jcsm.aasm.org/doi/10.5664/jcsm.8592),

2) “Detection of obstructive sleep apnea using Belun Sleep Platform wearable with neural network based algorithm and its combined use with STOP-Bang questionnaire” (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0258040),

3)Belun® Ring (Belun Sleep System BLS-100): Deep Learning-Facilitated Wearable Enables OSA Detection, Apnea Severity Categorization, and Sleep Stage Classification in Patients Suspected of OSA  (https://journals.lww.com/jhypertension/Abstract/2023/06000/The_Belun_sleep_platform_to_diagnose_obstructive.16.aspx), 

4) Correlation of Pulse Rate Variability(PRV) and Heart Rate Variability(HRV) Metrics During Sleep in Subjects Suspected of OSA (Accepted in SLEEP conference 2023, Abstract ID: 954).

If you would like to know more about how to adopt Belun’s solution in your organization or home use, please feel free to contact us to schedule a meeting by filling out the form below:

The post Sharing with Clinical Psychologists of HK’s Public Hospital first appeared on Belun Technology.