Correlation of Preoperative Global Olfactory Function With Frailty, Perioperative Neurocognitive Disorders and Mortality

Overview

The aims of this research project are to evaluate whether global olfactory impairment is a reliable indicator of preoperative frailty and cognitive impairment, and whether it may predict postoperative neurocognitive disorders, morbidity and mortality in a population of older patients scheduled for elective intermediate- to high-risk elective surgery. 1. We will measure preoperative global olfactory function (threshold, discrimination, identification) and evaluate whether olfactory impairment predicts preoperative frailty (using the Edmonton Frail Scale, the Clinical Frailty Scale and handgrip strength) and postoperative complications and mortality. 2. We will address the question whether preoperative olfactory impairment may be associated with a preoperative cognitive impairment (through a neuropsychological test battery) and whether it may predict a decrease in postoperative neurocognitive function.

Olfactory impairment increases with age, affecting more than 50% of the population aged between 65 and 80 years old. Recently, many studies have demonstrated a strong association between olfactory impairment and overall mortality risk. At the moment, the underlying physiopathology linking olfactory impairment to mortality remains unknown and only putative mechanisms are suggested. Among them, accelerated physiological brain aging seems to be involved, making olfactory decline a possible marker of frailty. To date, only a few studies (mostly using subjective olfactory assessment) investigated the potential relationship between olfactory impairment and frailty. Moreover, neurodegenerative diseases, through cognitive dysfunction, seem likely to represent a second mechanism potentially underlying the link between olfactory impairment and mortality. Surgery, and more broadly the perioperative period, remains a major source of morbidity and mortality. Meanwhile, the average age of the surgical population continues to rise, making preoperative risk assessment an essential step in order to detect the most vulnerable patients. Yet, it is well-known that frailty is predictive of complications and mortality and that preoperative cognitive impairment is associated with postoperative neurocognitive disorders. The first objective of this research project is thus to evaluate global olfactory function of preoperative older surgical patients in light of an assessment of their frailty and cognitive status. Frailty will be tested with the Edmonton Frail Scale, the Clinical Frailty Scale and handgrip strength. Cognitive function will be tested through a neuropsychological test battery preoperatively and postoperatively. The second and third objectives are to correlate preoperative olfactory function with, on the one hand, postoperative neurocognitive disorders, and on the other hand, postoperative morbidity and mortality.