Serum NfL levels have been found to positively correlate with the apnea, hypopnea and 4%-oxygen desaturation indices in addition to the percent of total sleep time with oxyhemoglobin saturation below 90%, but these correlations were mostly driven by moderate-to-severe OSA patients (Arslan et al., 2021). Here, NEFL is linked to obstructive sleep apnea syndrome.