CDK5 and obstructive sleep apnea syndrome: In this investigation, we recruited AD-OSA-M and AD-OSA-MS patients, assessed their cognitive function using various rating scales, measured the levels of AD biomarkers, CDK5, and synaptic proteins in CSF by enzyme-linked immunosorbent assay (ELISA), evaluated GMV and WMV by MRI, and conducted comparisons and correlation analyses among the aforementioned variables.