Examining the Longitudinal Relationship Between Olfactory Dysfunction and Frailty in Community-Dwelling, older US Adults

Objective. Olfactory dysfunction is a "canary in the coalmine" for aging conditions. We evaluated olfactory dysfunction as a biomarker of early frailty in older adults living in the United States. Study Design. Prospective, longitudinal, nationally representative study. Setting. National Social Life, Health and Aging Project (NSHAP). Methods. We examined data from 1061 community-dwelling older US adults. Odor identification (5-item Sniffin' Stick) and frailty scores were measured at baseline and 5-year follow-up. Multivariate logistic regressions evaluated the association between olfactory dysfunction and frailty at baseline in cross-section and over time in the transition from robust to prefrail to frail, adjusting for confounding factors measured at baseline. Results. Older US adults who were anosmic at baseline were more likely to be frail 5 years later compared to normosmic peers (odds ratio [OR]: 3.83, 95% confidence interval [CI]: 1.10-13.31, P = .035). Examining changes in frailty stage over time, we found that anosmics were more likely to transition from prefrail to frail over 5 years (OR: 3.25, 95% CI: 1.31-8.08, P = .011). Interestingly, hyposmics did not show a similar trajectory toward frailty (P > .05). In contrast, olfactory dysfunction was not associated with frailty in cross-section (OR: 0.90, 95% CI: 0.43-1.89, P = .787, hyposmia; OR: 0.72, 95% CI: 0.15-3.35, P = .673, anosmia). Conclusion. Older US adults with anosmia face higher odds of becoming frail over 5 years, especially those in the prefrail stage. Olfactory dysfunction may serve as a surrogate marker for early-stage neurodegenerative diseases, which are strong contributors to frailty.