Study to assess the prevalence of central sleep apnea in patients with heart failure with reduced or mildly reduced left ventricular ejection fraction (LVEF <50%) followed by case-control study to assess the link between central sleep apnea and cognitive function

The study will be conducted in two phases: prevalence phase and cognitive phase.

Adult patients with HFrEF/HFmrEF will perform a home sleep apnea test (HSAT). Patients will be assigned to one of the following groups based on their sleep study results: CSA, other SDB, or no SDB. This constitutes the prevalence phase of the study.

The cognitive phase of the study is a case-control study that will assess cognitive function in 20 patients in the CSA group (case) and 20 patients in the no SDB group (control).

Prevalence Phase Inclusion Criteria:

1. Diagnosed with heart failure with reduced or mildly reduced left ventricular ejection fraction (LVEF <50%) at least 3 months prior to enrollment
2. New York Heart Association (NYHA) functional class II-IV
3. Treated and optimized on heart failure guideline directed medical therapy as indicated for at least 4 weeks, including angiotensin receptor-neprilysin inhibitors (ARNI) (or angiotensin converting enzyme inhibitors (ACEI) or angiotensin receptor blocker (ARB)), aldosterone receptor antagonists, beta-blockers and/or sodium glucose co-transporter 2 (SGLT-2) antagonists
4. Age 50 years or older
5. Signed Institutional Review Board (IRB) or Ethics Committee (EC) approved informed consent
6. In the opinion of the investigator, subject is willing and able to comply with the protocol, including the cognitive function assessment

Prevalence Phase Exclusion Criteria:

1. Hospitalized for heart failure-related complications in the last 4 weeks
2. History of SDB and/or prior or ongoing treatment for SDB or tested for SDB within the prior year

Cognitive Phase Inclusion Criteria:

1. AHI ≥ 15 events per hour and CAHI ≥ 50% of total AHI (Case group) or AHI < 5 events per hour (Control group) based on the baseline HSAT
2. Per the patient and investigator, willing and able to postpone CSA treatment until completion of the study assessment visit (Visit 3)

Cognitive Phase Exclusion Criteria:

1. Color blindness
2. Currently taking opioids
3. Has taken medications for memory/cognition within the last 3 months (including but not limited to cholinesterase inhibitors and/or glutamate regulators)
4. Cerebrovascular accident (stroke or transient ischemic attack) in the last 12 months
5. Diagnosed with neurological disease including but not limited to history of seizures, meningitis, traumatic brain injury, amyotrophic lateral sclerosis, multiple sclerosis, attention-deficit/hyperactivity disorder (ADHD) or autism.

Adult patients 50 years or older with HFrEF/HFmrEF and no history of sleep disordered breathing (SDB) and not tested for SDB within the prior year will be tested for sleep apnea using a home sleep apnea test (WatchPAT device).