Postoperative Cognitive Dysfunction in Elderly and it's Relation With Sleep Disorders and Melanin Concentrating Hormone

Perioperative neurocognitive disorders (PNDs) have gradually become a priority during the perioperative period, including neurocognitive disorder before surgery, delirium and delayed neurocognitive recovery (DNR) within 30 days after surgery, and postoperative neurocognitive disorder up to 12 months after surgery. The incidence of DNR ranges from 9.1% to 45%, which seriously affects the perioperative brain health of older adult patients .

The increasing aging population and the reduced function and compensatory capacity of various systems in elderly patients also significantly increase the risk of cognitive dysfunction .

Sleep disorders are critical risk factors among the various risk factors for DNR after surgery. Meanwhile, aging is an independent risk factor for sleep disorders .

Therefore, it is clinically significant to conduct early cognitive risk prediction, focusing on older adult patients with preoperative sleep disorders. Studies have explored the risk factors for perioperative sleep disorders, while other studies have also explored the risk factors affecting postoperative cognitive outcomes. However, no study has explored the specific risk factors for DNR in patients with preoperative sleep disorders. Considering the relationship between sleep and postoperative cognitive function, especially in older adult patients, it is necessary to link these 2 main risk factors (preoperative sleep disorders and DNR) that impair the perioperative brain health to explore potential biomarkers .

Melanin-concentrating hormone (MCH) is a highly conserved cyclic neuropeptide with 19 amino acids in mammals and has a variety of physiological functions, including orexigenic properties, energy homeostasis, regulation of moods, sleep, wakefulness, and cognitive functions .

Melanin-concentrating hormone (MCH) can enhance synaptic plasticity in the hippocampus, which plays an important role in maintaining cognitive function In addition to regulating synaptic plasticity, MCH can also regulate cognitive functions such as learning and memory by regulating rapid eye movement (REM) sleep and acetylcholine outflow in the hippocampus .

Inclusion criteria

• 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

Exclusion criteria

• 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.
• Inability to understand or cooperate with the evaluation scale or questionnaire.
• Refuse collecting one's own CSF and blood samples.