Olfactory Dysfunction Predicts Subsequent Dementia in Older U.S. Adults

Abstract

Objectives To investigate the relationship between olfactory dysfunction and subsequent diagnosis of dementia. Design Longitudinal study of a population representative of U.S. older adults. Setting Home interviews (National Social Life, Health, and Aging Project). Participants Men and women aged 57 to 85 (N = 2,906). Measurements Objective odor identification ability was measured at baseline using a validated five‐item test. Five years later, the respondent, or a proxy if the respondent was too sick to interview or had died, reported physician diagnosis of dementia. The association between baseline olfactory dysfunction and an interval dementia diagnosis was tested using multivariate logistic regression, controlling for age, sex, race and ethnicity, education, comorbidities (modified Charlson Comorbidity Index), and cognition at baseline (Short Portable Mental Status Questionnaire). Results Older adults with olfactory dysfunction had more than twice the odds of having developed dementia 5 years later (odds ratio = 2.13, 95% confidence interval = 1.32–3.43), controlling for the above covariates. Having more odor identification errors was associated with greater probability of an interval dementia diagnosis (P = .04, 1‐degree of freedom linear‐trend test). Conclusion We show for the first time in a nationally representative sample that home‐dwelling older adults with normal cognition and difficulty identifying odors face higher odds of being diagnosed with dementia 5 years later, independent of other significant risk factors. This validated five‐item odor identification test is an efficient, low‐cost component of the physical examination that can provide useful information while assessing individuals’ risk of dementia. Use of such testing may provide an opportunity for early interventions to reduce the attendant morbidity and public health burden of dementia.

Predictive value of olfactory impairment for cognitive decline among cognitively normal adults

“…In one study with 5 years of follow‐up time, those with OI compared to those without OI at baseline had a significantly increased odds of developing incident dementia (adjusted OR = 2.13, 95% CI 1.33–3.69) . In another study, decrease in the 13‐item SOIT score was associated with higher risk of developing dementia at 10 years (adjusted OR = 1.12, 95% CI 1.02–1.23) .…”

“…One of these determined incident dementia using clinical diagnosis with Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM‐IV), criteria . Another study used medical record abstraction and/or ≥1.5 SD decline in Modified MMSE compared with cohort's race‐matched mean change in score, whereas the third study used self‐ or proxy‐reported diagnosis of dementia …”

“…32 UPSIT is a 40-item battery of microcapsules paired with multiple-choice questions for scent identification that was originally validated for use in North America, but since then it has been shown to have validity in many other countries. The scores were evaluated as continuous, 18,22,25,30,33 categorical, 19,21,23,24 or both. 20 Categories were race-and sex-stratified tertiles, 24 manufacturer manual-based binary definitions of microsomia and anosmia, 20,30 or with olfactory dysfunction defined a priori.…”

“…However, this study included only two longitudinal cohort studies, precluding strong conclusions about the predictive utility of olfactory impairment . Several longitudinal studies have been published since 2012 that support the predictive value of olfactory testing in future cognitive decline …”

“…17 Several longitudinal studies have been published since 2012 that support the predictive value of olfactory testing in future cognitive decline. [18][19][20][21][22][23][24][25] To examine the association between olfactory impairment and future cognitive decline or incident dementia, we performed a systematic review and quality assessment of longitudinal studies following cognitively normal adults with baseline OI in comparison to those without OI.…”