The Association of Peripheral and Central Olfaction With Frailty in Older Adults

Background Olfactory impairment is increasingly recognized as a biomarker of frailty, but the relationship between olfactory subdomains that describe peripheral or central dysfunction and frailty remains unexplored. Methods We examined 1 160 older adults from the National Social Life, Health, and Aging Project Wave 3. Olfactory identification (OI): the ability to identify an odorant; and olfactory sensitivity (OS): the ability to detect the presence of an odorant, were assessed using 5- and 6-point measures, respectively. Frailty was operationalized as both a 37-item frailty index (FI) and the 5-item Physical Frailty Phenotype (PFP). Mixed models were fit to examine the association between OI, OS, FI, and PFP, while adjusting for demographic and clinical covariates. Results Participants in the most-frail PFP category had lower OI and OS scores (OI: 3.88 vs 4.19, p = .016; OS: 3.15 vs 3.47, p = .031), whereas participants in the most-frail FI category exhibited lower OI scores but not OS scores when compared to nonfrail participants (OI: 3.72 vs 4.27, p = .014; OS: 3.19 vs 3.43, p = .476). Adjusted mixed models showed that a point increase in OI was associated with a lower PFP score (β = −0.107, p = .006) and FI score (β = −0.009, p = .010). A point increase in OS was associated with a lower PFP score (β = −0.058, p = .016) but not FI score (β = −0.004, p = .064). Conclusion Both OS and OI, predominantly peripheral and central measures of olfaction, respectively, are associated with frailty implicating olfaction as a potential biomarker and risk factor for frailty.