Obstructive sleep apnea (OSA) is a common but underdiagnosed and undertreated sleep disorder among people with epilepsy (PWE). In PWE, this sleep disorder is often managed as a comorbid condition rather than a contributor to epilepsy outcomes. For many years, OSA has been associated with higher seizure burden and interictal epileptiform discharges. Emerging evidence links OSA to late onset epilepsy (LOE) and increased risk markers for sudden unexpected death in epilepsy (SUDEP). This evidence also suggests that treating OSA with continuous positive airway pressure may improve seizure control. This critical review of the literature posits that OSA should be viewed as a modifiable risk factor for PWE. We apply the Bradford Hill criteria for causation as a framework to appraise the evidence connecting OSA with (1) seizure severity, (2) incident LOE, and (3) SUDEP risk. OSA supports eight of nine Bradford Hill criteria to varying degrees: strength, consistency, temporality, biological gradient, plausibility, coherence, analogy, and experiment, but not specificity. Key limitations include confounding, selection and adherence biases, and limited randomized evidence. However, the evidence supports integrating systematic OSA screening and evidence-based treatment into epilepsy care. Future research should prioritize randomized trials to assess the impact of OSA treatment on epilepsy incidence, severity, and SUDEP risk.

Epilepsy is a heterogeneous neurological disorder affecting more than 70 million people worldwide, posing significant challenges for clinicians due to its complex etiology, diverse manifestations, variable treatment responses, and the inability to predict seizures or disease onset reliably. Despite advances in antiseizure medications, approximately 30% of patients remain treatment-resistant, highlighting the urgent need for therapies with antiepileptogenic or disease-modifying effects. To optimize and individualize strategies to predict and treat seizures and epilepsy, efforts to identify biomarkers of epilepsy risk, epileptogenesis, seizures, and therapy response are ongoing. This article reports key presentations and discussions from the 2023 Workshop on Neurobiology of Epilepsy (WONOEP XVII) in Kilkea, Ireland on novel epilepsy biomarkers and treatment strategies beyond the synapse and does not constitute a comprehensive review of biomarkers or treatment strategies. Much of the focus in epilepsy research has centered on identifying primarily neuronal processes or components. The 2023 WONOEP presentations discussed advances in plasma biomarkers for posttraumatic seizures and outcomes, perivascular spaces in posttraumatic epilepsy and poststroke epilepsy, imaging biomarkers of astrogliosis, and plasma microRNA biomarkers of intellectual disability and autism in tuberous sclerosis complex. Furthermore, research on immuno- and anti-inflammatory therapies and blood-brain barrier in drug-resistant focal epilepsies and infantile epileptic spasms syndrome was presented, as well as on the effects of antiseizure and cardioprotective medications on cardiac injury in temporal lobe epilepsy. The review also emphasizes the need for further interdisciplinary collaboration to accelerate the translation of these findings into clinical practice, ultimately improving outcomes and quality of life for people with epilepsy.