The aim of this study is to explore the relationship between preoperative sleep disorders, melanin-concentrating hormone (MCH), and delayed neurocognitive recovery early after surgery in older adult patients undergoing spinal anesthesia.
Patients of both genders ageing 65 years or above.
ASA grade I to III.
Undergo elective lower limb surgery under spinal anesthesia
Agree to collect one's own CSF and blood samples
Past history of depression,anxiety,delirium and schizophrenia .
Past history of drug dependence.
Past history of dementia,including Alzheimer disease(AD).
Preoperative Montreal Cognitive Assessment (MoCA) score <26.