[Interview] ‘Obstructive sleep apnea is a whole-body disease, not a sleep issue’

“When oxygen supply drops during sleep, the sympathetic nervous system becomes hyperactive, causing frequent awakenings throughout the night. The heart also begins to beat excessively hard.”

Professor Lee Seung-hoon of the Department of Otolaryngology at Korea University Ansan Hospital said so, explaining the dangers of obstructive sleep apnea (OSA). He stressed that OSA is more than just “snoring”—it is a serious systemic disease that can lead to life-threatening conditions such as myocardial infarction, ischemic heart disease, and stroke.

“The reason you feel excessively sleepy in daily life and have poor concentration during the day is ultimately due to that repeated arousal,” he said.

As Professor Lee explained, the impact of OSA extends well beyond sleep quality—OSA not only diminishes an individual's quality of life but also substantially raises the risk of societal accidents, such as drowsy driving caused by sleep deprivation.

The most common reason OSA patients seek medical help remains “snoring noise.” This is because it disturbs family members' or partners' sleep, leading to complaints. However, according to Professor Lee, the more significant clinical issues are the “fatigue” and “daytime sleepiness” experienced by patients themselves.

When obstructive sleep apnea (OSA) is present, oxygen supply during sleep decreases. To compensate, the sympathetic nervous system—the system responsible for activating the body's 'fight or flight' response—becomes overactive, frequently waking the brain. As a result, deep sleep is disrupted, leading to repeated awakenings. This causes chronic fatigue and impaired concentration. In addition, repeated oxygen deprivation puts extra strain on the heart. Over time, this can cause abnormal heart rhythms (arrhythmias) and increased myocardial stress (pressure or workload on the heart muscle). These changes are known to increase the risk of various cardiovascular complications.

“Individuals who frequently wake during sleep fail to achieve restorative rest, sharply increasing the risk of drowsy driving during daytime hours,” Professor Lee noted. “Particularly for truck drivers who frequently engage in long-distance driving or night shift workers, the risk of accidents due to sleep apnea has been reported to increase significantly.”

In summary, OSA is a serious health condition that significantly increases both individual and societal health risks.

OSA rises steeply alongside obesity

Obesity is known to be a major cause of OSA, and the link between the two is clearly observed in clinical practice. “I frequently see newlywed patients who report that their snoring worsened after gaining weight following marriage,” Lee testified.”

Weight gain increases fat around the uvula and soft palate. Under gravity, this fat sags backward, narrowing the airway. Fat on the tongue can further constrict the airway, increasing OSA risk. In other words, as the neck circumference increases, the internal airway gets smaller.

Indeed, the prevalence of OSA in Korea is already high. According to a 2004 cohort study conducted by Korea University Ansan Hospital, 27 percent of men and 16 percent of women had an Apnea-Hypopnea Index (AHI) of 5 or higher. The clinical prevalence of OSA, considering daytime sleepiness, was reported as 4.5 percent for men and 3.2 percent for women.

Furthermore, the number of diagnosed patients began to increase significantly after health insurance coverage for polysomnography and CPAP therapy started in 2018. The number of diagnoses, previously around 20,000 to 30,000 per year, rose to 45,000 in 2018, the first year of coverage. After a decline in hospital visits during 2020-2022 due to Covid-19, the number increased rapidly again post-pandemic, reaching around 180,000 per year as of 2024.

Professor Lee explained this trend as “the result of systematically rising diagnosis rates due to improved test accessibility,” adding, “This means many more hidden patients are being identified compared to the past.”

Limitations of CPAP therapy -- effective only when actually used

The current standard treatment for OSA is continuous positive airway pressure (CPAP or PAP). It works by using positive pressure to prop open the collapsing upper airway, maintaining breathing, and its therapeutic effect is clear. Patient costs have also decreased significantly since the introduction of health insurance coverage. For a polysomnography test costing around 800,000 won, the patient's out-of-pocket expense is only 20 percent. For automated CPAP devices, the patient pays 50 percent for the first three months, and if compliance criteria are met, the out-of-pocket cost drops to just 20 percent thereafter.

Nevertheless, treatment compliance inevitably declines over time. Professor Lee likened this to eyeglasses. Just as glasses only provide clear vision while worn, CPAP only improves breathing and sleep quality during use. In other words, stopping use causes the effects to vanish immediately.

Professor Lee stated, “Long-term CPAP compliance drops to about 60 percent, meaning only half the patients actually sustain the therapeutic benefits,” adding, “This necessitates alternative treatment options for the remaining patients who struggle with CPAP use.”

To address this gap, surgical treatment is sometimes performed. This involves cutting the uvula and soft palate to widen the upper airway. The average success rate is around 50-55 percent, but it varies a lot depending on the patient’s anatomy. Because of this, the need for non-surgical, drug-based treatment is often raised.

Mounjaro’s arrival signals a paradigm shift in OSA treatment

A breakthrough came last year when Mounjaro (tirzepatide), a well-known obesity treatment, became the first drug to obtain an OSA indication.

“It was striking that the slogans ‘From CPAP to Pharmaceutical therapy’ and ‘First Medical Medicine’ appeared at this year's World Sleep 2025 conference,” Lee noted. “This is a clear example showing that drug therapy is emerging as a new weapon in treating sleep apnea.”

Mounjaro is gaining attention because of the obesity–OSA link. Studies have shown that weight loss can improve OSA. This relationship was confirmed by new research in the New England Journal of Medicine. A 20 percent BMI reduction led to a 57 percent improvement in AHI.

In clinical trials, Mounjaro demonstrated an average weight loss of 17-20 percent alongside a 50-58 percent improvement in AHI, making it the first treatment strategy capable of simultaneously addressing both obesity and OSA.

In the SURMOUNT-OSA 1 and 2 clinical trials, Mounjaro significantly reduced AHI in both CPAP users and non-users. Up to 72.4 percent achieved a 50 percent or greater reduction in AHI. Up to 50.2 percent improved to “AHI <5” or to “mild asymptomatic levels (AHI 5–14, ESS≤10).”

However, he drew a line against prescribing Mounjaro to all OSA patients.

He explained that the indication for Mounjaro requires “BMI ≥30 kg/m² plus moderate to severe OSA.” This is for precise targeting. It helps prevent drug overuse and maximizes clinical benefit.

CPAP therapy remains the standard treatment for OSA. However, weight loss is the core treatment for OSA that co-occurs with obesity. Professor Lee stated, “In clinical practice, we emphasize lifestyle changes first.” He added, “However, few patients achieve enough weight loss with exercise and dietary control alone.”

Appetite control is difficult, and existing weight loss medications are not sufficiently effective. In this regard, Mounjaro has become a new option for OSA treatment, as noted.

“Medication does not have to be the first step. It is suitable for patients with a BMI of 30 kg/m² or higher who cannot lose weight despite lifestyle changes,” Professor Lee said. “For patients with low compliance to CPAP therapy, Mounjaro can be an important alternative.”

Insurance coverage remains a challenge

Currently, Maunjaro's OSA indication can only be prescribed as a non-covered benefit.

“The cost is a big burden for patients. But when you consider the potential heart issues or accident risks from untreated OSA, the social cost can be even greater,” Professor Lee said. “Discussion at the government level is needed. More research is also essential.”

Based on actual clinical experience, he projected, “Among the approximately 130,000 patients diagnosed annually in Korea, those with a BMI of 30 or higher are estimated to be about 20 percent. As obesity increases in the future, the number of patients eligible for prescription is likely to gradually rise.”

Professor Lee noted, “Current research on various obesity treatments is expanding beyond traditional weight loss and cardiovascular improvement into broader areas like OSA.” He projected that the development of diverse OSA medications, including oral formulations, could create new opportunities to expand the patient base eligible for treatment and reduce cost barriers.

Currently, Mounjaro holds immense clinical significance as the first officially recognized OSA drug therapy—a milestone that could transform treatment, especially by enabling care tailored to individual factors such as weight, cost, and compliance.