1. What is the CAPNETZ project, and why is community-acquired pneumonia such an important field of research?

Community-acquired pneumonia (CAP) remains one of the most common infectious diseases, associated with significant morbidity, mortality, and healthcare costs. The CAPNETZ project was launched more than 20 years ago to better understand the epidemiology, risk factors, distribution of pathogens, treatment, and long-term course of CAP, and thereby improve care for CAP patients. The project is a German patient registry¹ that prospectively enrolls patients with community-acquired pneumonia, documents clinical data, findings, treatment, and outcomes, and collects samples for further analysis (Biobank). ¹The CAPNETZ Registry is a digital platform accessible to all participating clinics. There are also “in-person” employees based in Hanover, and of course the clinical investigators located throughout Germany. For more information, visit capnetz.de

2. You have discovered that sleep apnea may be a risk factor for severe pneumonia. How did this realization come about? 

The observation that sleep apnea (sleep-disordered breathing, SDB) may be associated with a more severe course of community-acquired pneumonia (CAP) is based on an analysis we conducted using the aforementioned prospective CAPNETZ cohort. Our study included 4,686 patients with CAP for whom information was available regarding a prior diagnosis of SDB and any CPAP therapy. Incidentally, sleep-disordered breathing (SDB) had been diagnosed in only 2.6% of participants, and just 1.6% were receiving CPAP therapy. Our analysis then showed that patients with sleep apnea were admitted to the intensive care unit significantly more often and required invasive ventilation more frequently than comparison patients without sleep apnea. Even after adjusting for all classic risk factors for severe CAP (e.g., age, sex, comorbidities such as diabetes, initial severity of pneumonia, and vital signs), sleep apnea remained an independent predictor of severe CAP. Fortunately, this did not affect the 28-day mortality rate, which may indicate that all parties involved are paying closer attention to the treatment of patients with SDB and CAP. Interestingly, however, patients with SBD who were undergoing CPAP therapy did not show an increased risk of severe CAP.

3. What happens inside of the body during sleep apnea – and how might it complicate the course of pneumonia? 

It has been known for many years that patients with SDB have a significantly increased risk of cardiovascular disease and higher mortality rates. We are now beginning to gain a better understanding of the underlying pathophysiological mechanisms: Sleep-related breathing disorders lead to repeated episodes of nocturnal hypoxemia, arousals, and marked fluctuations in intrathoracic pressure. These events trigger a series of secondary processes, including increased sympathetic tone and fragmented sleep, which affect a variety of neurohumoral regulatory circuits. However, these pathophysiological changes affect more than just the cardiovascular system. A growing body of evidence suggests that they also affect the immune system and, consequently, the body’s ability to fight off infections. Studies show that patients with OSA exhibit increased systemic and local inflammatory activity, characterized by elevated cytokine release, increased oxidative and endothelial stress, and impaired mucociliary clearance. Given this context, it seems plausible that SDB may also have an adverse effect on the risk and course of pneumonia. Repeated episodes of nocturnal hypoxia lead to chronic inflammation, which can weaken the body’s antiviral and antibacterial defenses. In addition, nocturnal oxygenation is already impaired in these patients, so they have less respiratory capacity on reserve in the event of an acute pulmonary infection. In addition, there is an increased risk of microaspiration – especially in cases of obesity or gastroesophageal reflux – which further contributes to the development and progression of severe respiratory infections.

4. How common is sleep apnea in the general population, and in your opinion, is it being adequately diagnosed and treated?

Sleep apnea is widespread among the general population – most cohort studies estimate that about 10 to 20 percent of adults are affected to varying degrees, with men being affected more frequently than women. Its prevalence increases markedly with advancing age and excess body weight. Despite this high prevalence, the condition often goes undiagnosed. Many people with this condition are unaware that they experience repeated pauses in breathing while they sleep, as typical symptoms such as loud snoring or daytime sleepiness are often not taken seriously or are attributed to other causes.

5. What do your research findings specifically mean for family doctors, nurses, and patients? Are there any simple steps that might help? 

Regardless of our data, primary care physicians should always consider sleep apnea in patients with risk factors – such as obesity, loud snoring, observed breathing pauses, or excessive sleepiness during the daytime – since it appears to affect both quality of life and prognosis. A simple outpatient screening – even if it involves using any approved wearables – can help kick off the diagnostic evaluation. Based on our data, however, our colleagues should now also pay closer attention to patients with recurrent respiratory infections or more severe disease progression who have the aforementioned risk factors, considering SBD as a possible comorbidity. Nurses can also make an important contribution by watching for typical signs in our pneumonia patients – such as restlessness at night, pauses in breathing, or extreme daytime fatigue – and reporting these observations. However, the fact that this patient group in our study fortunately did not exhibit any short-term excess mortality leads me to believe that well-trained nursing staff and excellent interdisciplinary collaboration are already commonplace in their daily practice. For those affected, simply having a better understanding of the condition can make all the difference: Weight management and consistent use of prescribed CPAP therapy are simple yet effective measures. If sleep apnea is detected and treated early, it can not only improve sleep quality and overall well-being, but may also help prevent severe cases of infections such as pneumonia.

6. What role does interdisciplinary collaboration – between pulmonologists, sleep medicine specialists, and primary care physicians, for example – play in putting such findings into practice? 

Interdisciplinary collaboration plays a central role in translating our findings into clinical practice, but it is often challenging in day-to-day work. Ideally, primary care physicians identify high-risk patients at an early stage and perform triage; pulmonologists and sleep medicine specialists then promptly diagnose and treat OSA. Unfortunately, the reality is often quite different: Structural and bureaucratic pressures on primary care physicians make it difficult to implement sleep apnea screening; furthermore, sleep labs in Germany do not have nearly enough capacity. Ultimately, this leads to exactly what we observed in the study: Despite an expected significantly higher prevalence, we see only 2.6% of patients with a prior diagnosis of sleep apnea. Improved coordination can certainly be supported by concrete measures such as joint guidelines or standardized algorithms, but in reality it will only succeed through changes to healthcare delivery systems and a greater focus on sleep medicine issues.

7. What's next for the CAPNETZ project? Are there any new research questions you’re currently exploring? 

There are indeed already many ideas here: It would be great to systematically screen patients for sleep apnea within the CAPNETZ program in order to scientifically evaluate the significance of individual functional parameters such as the apnea-hypopnea index, hypoxic burden, heart rate variability, sleep fragmentation, etc. This is even possible now using simple wearables such as watches and rings, some of which are already approved for the diagnosis of sleep apnea. Of course, a major dream would be a large-scale interventional study: Can post-acute treatment for sleep apnea following hospital discharge prevent pneumonia from recurring? Does it make sense to screen hospital patients for breathing pauses at the outset and, if necessary, treat them with CPAP or high-flow oxygen therapy while they are still in the hospital to prevent severe disease progression? Maybe Löwenstein still has a little money left over to fund a study like that … ;-)

8. What do you expect from the public and the healthcare system to help put such research findings into practice more effectively?

We spend about one-third of our lives sleeping. With this in mind, I believe that sleep medicine deserves more attention from the various medical societies and also needs a much stronger voice in the political arena. Diagnosis and treatment in the field of sleep medicine have now become a domain of outpatient care. This is certainly a valid point, but we must be careful not to lose even more capacity for treatment as a result, and we have to maintain the necessary quality standards and keep on providing training for the next generation. There is a lot of talk about the shortage of family doctors in rural areas. If we can also manage to draw a little attention to the importance of sleep medicine – especially given the current lack of care capacity – we would certainly be a big step closer to our goal.

Professor Bitter, thank you very much for the interview. 

Here you will find the abstract from the ERS Congress.