This study aimed to evaluate the clinical and neuroimaging correlates of obstructive sleep apnea (OSA) in adults with late-onset unexplained epilepsy (LOUE).

We prospectively recruited adults with LOUE (unexplained seizure after age 55) who underwent polysomnography or home sleep testing as part of their clinical care. Participants were dichotomized into no/mild OSA (apnea-hypopnea index [AHI]<15) and moderate/severe OSA (AHI≥15) groups. We evaluated their plasma phospho-tau-217 (ptau-217) levels and extracted seizure semiology variables, SSRI/SNRI use, and number of anti-seizure medications (ASMs). Participants also underwent magnetic resonance imaging (MRI), and we quantified their hippocampal and amygdala volumes using FreeSurfer.

Of the 85 enrolled participants, 31 underwent sleep testing, and 2 were excluded due to a prior diagnosis and treatment of OSA. The final cohort (n=29) had a mean age of 69.89±6.66 years and was 45% female. 15 participants (51.7%) had no/mild OSA and 14 (48.3%) had moderate/severe OSA. The mean time between sleep study and MRI was 1.5 years. After controlling for age and sex, participants with moderate/severe OSA were more likely to be on an SSRI/SNRI (OR=65.93, p=0.020), less likely to present with a nocturnal generalized tonic-clonic seizure (GTCS, OR=0.082, p=0.038), and had lower total amygdala volumes (β=-0.00027, p=0.049) relative to those with no/mild OSA. There were no significant differences in ptau-217 levels (p=0.89) or ASM number (p=0.45) between the two groups.