Potential Risk to Brain Health after Surgical Interventions: Biomarkers to Predict the Occurrence of Cognitive Decline

As the global population ages, the number of people living with dementia is projected to increase significantly. Estimations indicate that over 150 million people worldwide will be living with dementia by 2050, with Alzheimer's disease being the most common cause. Elderly people are also at greater risk of undergoing surgery, either elective or emergency, escalating the associated likelihood leading to cognitive decline, especially if accumulative. However, the relationship between surgery and dementia development remains controversial. The cause seems to lie in the heterogeneous preoperative state of subjects participating in research studies. Interpreting and comparing the results of these studies could be an arduous task due to variables such as medication, follow-up time, type of surgery and anesthesia, duration and invasiveness of the surgical intervention, differential neuroinflammatory response, the patient metabolic/biochemical status or if there are comorbidities. Considering the complexity of this type of studies, the present review summarizes the most important factors/biomarkers that could provide useful information for pre- and post-operative medical decision making in relation to the development of dementia. Emphasis will be placed on the relationship between temperature, Tau phosphorylation, whose plasma detection as an early diagnostic factor is gaining great relevance, and other neurodegenerative biomarker interplay. The prolonged maintenance of key biomarkers in blood could be detrimental and, therefore, a more comprehensive individualized hospital study may improve the prevention of postoperative complications.