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.

Keywords: aged; dementia; longitudinal studies; olfaction disorders; smell.

Figure 1

Olfactory dysfunction (number of odor identification errors) predicts increased probability of physician dementia diagnosis five years later.