Obstructive sleep apnea in refractory epilepsy: A pilot study investigating frequency, clinical features, and association with risk of sudden unexpected death in epilepsy

Abstract

Objective: We aimed to determine the frequency of probable obstructive sleep apnea (pOSA) in refractory epilepsy monitoring unit inpatients and clinical features associated with pOSA, including risk for sudden unexpected death in epilepsy (SUDEP).

Methods: We prospectively recruited 49 consecutive adult patients admitted to the Mayo Clinic Epilepsy Monitoring Unit with focal, generalized, or unclassified epilepsy syndromes. pOSA was identified using oximetric oxyhemoglobin desaturation index (ODI) and the Sleep Apnea-Sleep Disorders Questionnaire (SA-SDQ) and STOP-BAG screening tools. Revised SUDEP Risk Inventory (rSUDEP-7) scores were calculated, and epilepsy patients with and without pOSA were compared with Wilcoxon signed-rank tests. Correlation and regression analyses were utilized to determine relationships between pOSA and rSUDEP-7 scores.

Results: Thirty-five percent of patients had pOSA, with a mean ODI of 11.3 ± 5.1/h (range = 5.1-22.8). Patients with pOSA were older and heavier, and more frequently had a focal epilepsy syndrome and longer epilepsy duration, with higher SA-SDQ and STOP-BAG scores (all P < 0.05). Median rSUDEP-7 score was 3 ± 1.4 (range = 0-6). Higher rSUDEP-7 scores were positively correlated with higher ODI (P = 0.036). rSUDEP-7 score ≥ 5 was associated with pOSA by ODI, SA-SDQ, and STOP-BAG questionnaire criteria (P < 0.05).

Significance: Our pilot study identified a high frequency of pOSA in refractory epilepsy monitoring patients, finding that pOSA patients were older and heavier, with higher screening symptoms for sleep apnea and more frequent focal seizures with a longer epilepsy duration. We also found a possible association between OSA and SUDEP risk. Identification and treatment of OSA in patients with epilepsy could conceivably provide a novel approach toward preventing the risk of SUDEP. Future studies with polysomnography are needed to confirm predictive features for OSA in epilepsy populations, and to determine whether OSA is associated with SUDEP risk.

Keywords: SUDEP-7; epilepsy; obstructive sleep apnea; revised SUDEP-7; sudden unexpected death in epilepsy.

Figure 1. Two portable overnight oximetry profiles

from (A) an epilepsy patient with a normal oxyhemoglobin desaturation index of < 1/ hour, and (B) an epilepsy patient with an ODI of 6/hour, showing several clustered oscillatory desaturations typical of mild obstructive sleep apnea.

Figure 1. Two portable overnight oximetry profiles

from (A) an epilepsy patient with a normal oxyhemoglobin desaturation index of < 1/ hour, and (B) an epilepsy patient with an ODI of 6/hour, showing several clustered oscillatory desaturations typical of mild obstructive sleep apnea.

Figure 2. Relationship Between rSUDEP-7 Risk Profile and Adjusted ODI.

Shown is the association between SUDEP risk profile as indexed by scores on the rSUDEP-7, and the adjusted oxyhemoglobin desaturation index, where scores >5/hour are consistent with probable obstructive sleep apnea.