Part 3: Registries shaping sleep apnea care in Europe

In this interview, Professor Grote discusses the role of national and European registries in advancing sleep apnea care. He explains how Sweden’s SESAR registry supports implementation of its national treatment matrix, and why the pan-European ESADA project can help health systems with patient prioritization.

Q. A unique element in Sweden is the existence of the Swedish Sleep Apnea Registry (SESAR). Could you describe what SESAR is?

Professor Grote: SESAR is one of about 100 Swedish national quality registries, each collecting key variables for specific diseases and their management. SESAR focuses on obstructive sleep apnea (OSA) diagnosis, treatment and follow-up. It includes data from more than 65 centers diagnosing and treating OSA, including some of the largest in the country, as well as dentists providing oral device therapy.

The idea is that both patients and centers can compare outcomes and procedures, learn from each other and identify best practices. SESAR collects data on variables such as apnea-hypopnea index (AHI), body mass index (BMI), Epworth Sleepiness Scale (ESS), mean saturation, wait times, treatment starts and procedural data and follow-up, particularly for positive airway pressure (PAP) therapy and oral devices.

This allows clinics to track trends in patient flows, treatment adherence, outcomes like AHI reduction or symptom improvement, and even the impact of mask type on PAP therapy adherence. In this way, clinics can systematically identify what management practices work best for patients.

Last year alone, we collected data on around 67,000 sleep apnea patient visits. In total, we are nearing 200,000 individual patients in the registry. On average, we capture an estimated 60–80 percent of OSA diagnoses and 80–90 percent of PAP treatment initiations.

Q. Why is SESAR useful when implementing changes like the new Swedish treatment matrix?

Professor Grote: We can always speculate and have strong opinions, but objective registry data allows for systematic analysis. In our annual reports, we include interviews with clinics that use SESAR data to improve their practice and routines. These clinics can compare their performance over the years and see how patient flows and outcomes have changed.

For instance, SESAR documents the use of nasal versus full-face masks at the start of treatment and how this affects compliance, AHI reduction and residual sleepiness. Having this kind of data and insight provides a strong incentive for individual clinics to work systematically on improving their routines.

Yet, while the registry can be used for research, its primary goal is to improve care and make results visible. Patients can even compare centers on the public website, which encourages transparency and quality improvement.

Q. What kind of trends are you expecting to see in SESAR data due to the new guidelines? Have you seen any changes already?

Professor Grote: From the guidelines, you would expect more referrals for symptomatic patients, fewer asymptomatic elderly patients and a lower mean age overall but, in reality, we are seeing the opposite. Patients coming in are older on average, and less sleepy. The average score on the ESS continues to drop year after year. This trend is not unique to Sweden; the European Sleep Apnea Database (ESADA) shows the same pattern.

This holds true for both major treatment groups: PAP therapy and oral appliances. Instead of treating more obviously sleepy patients, we are treating less sleepy ones. It is an interesting and somewhat unexpected finding, and we are still working out how to interpret it in relation to the goals of the matrix. It may be linked to increased referrals for cardiovascular comorbidities such as hypertension or atrial fibrillation, where sleepiness, as shown in other cohorts, is less prominent.

Another limitation is that the SESAR registry does not currently track other important, potentially treatable traits such as fatigue, morning headaches, or nocturnal sweating, so we cannot yet fully confirm the patient profiles. We definitely need more years of data collection to analyze these trends properly.

Q. You mentioned ESADA in relation to these trends. Could you explain what ESADA is and how it works?

Professor Grote: ESADA is a large collaborative project that was started back in 2007 by a group of European sleep apnea experts, and now includes nearly 40 sleep clinics across Europe. Together, these clinics have entered data on more than 45,000 patients with sleep apnea and nearly 80,000 visits. What makes ESADA special is that it’s not just a one-off snapshot, it’s a longitudinal database. Patients are included at their first evaluation for suspected sleep apnea and then monitored continuously with standardized reporting so researchers can look at outcomes over time.

Every patient is given an anonymous ID, and each center reports comprehensive data on them, including anthropometrics, symptoms, medical history, lab values, sleep study results, comorbidities and treatments. This data is then transferred to a centralized database at Gothenburg University using a uniform, web-based clinical report.

Q. Why is ESADA particularly important for identifying which patients should be prioritized for treatment?

Professor Grote: ESADA is important because it helps us move beyond national perspectives and look at OSA treatment on a much larger scale.

While registries like SESAR help refine care locally, ESADA brings together data across countries, health systems and patient populations in Europe. This breadth allows us to better understand sleep apnea phenotypes, regional practice differences and how comorbidities influence outcomes. Researchers will be able to see clear trends and patterns that a single clinic or even a single country may never have noticed on its own.

It also allows us to study longitudinal outcomes. That means we’re not only finding out how patients present initially, but also how they do after years of PAP therapy, oral devices, or even surgery — what works best, who sticks with treatment, and what improves blood pressure, glucose control or mortality risk. By identifying these subgroups early, ESADA can help health systems refine priorities. So instead of just treating everyone the same, we can better identify which patients should really be prioritized for care.

To learn more about the Swedish treatment matrix and how it has been received by physicians and sleep medicine specialists, read the first part of this three-part interview series with Professor Ludger Grote.