This study evaluates different factors that determine the treatment choice and treatment compliance in patients with central sleep apnea. All patients will receive routine care (registry).

Central sleep apnea (CSA) is characterized by intermittent cessation or decrease of airflow and effort of breathing during sleep. The diagnostic criteria for CSA varies according to the type of CSA (e.g. CSA due to cardiac failure, due to a medication, ...).

CSA is defined as: (1) an apnea/hypopnea index ≥ 15 per hour of sleep and (2) the number of central apneas and/or hypopneas is > 50% of the total number of apneas and hypopneas.

Presence of CSA is associated with excessive daytime sleepiness and poor sleep quality. Furthermore, in patients with heart failure, presence of CSA was found to be related to mortality. As yet, however, there is insufficient knowledge on the clinical features, pathophysiological background and consecutive algorithms for treatment. Currently, it is not fully clear whether CSA or the treatment of CSA is related to disease progress.

The aim of this trial is to evaluate the current treatment choices for CSA in Belgium and compliance with and effects of these treatments.

Inclusion Criteria:

• Age ≥ 18 years old
• An apnea/hypopnea index ≥ 15/h of sleep and proportion of non-obstructive events > 50%, derived from polysomnography (diagnostic or during (PAP) treatment)
• Written informed consent provided

Exclusion Criteria:

- Patients with mental disability making it impossible to understand the study protocol

Subjects with an apnea/hypopnea index ≥ 15/h of sleep and proportion of non-obstructive events > 50%, derived from polysomnography (diagnostic or during positive airway pressure treatment)