Association of Performance on Olfactory and Cognitive Screening Tests With Conversion to Dementia in a Biracial Cohort of Older Adults

Abstract

<h3>Background and Objectives:</h3> Odor identification deficits are associated with transition to dementia, whereas intact odor identification and global cognition test performance may identify lack of transition. The purpose of this study is to examine intact odor identification and global cognition as prognostic indicators of lack of transition to dementia in a biracial (Black and White) cohort. <h3>Methods:</h3> In a community-dwelling sample of older adults from the Health, Aging, and Body Composition (Health ABC) study, odor identification was measured using the Brief Smell Identification Test (BSIT) and global cognition was measured using the Teng Modified Mini-Mental Status Examination (3MS). Survival analyses for dementia transition over 4 and 8 years of follow-up utilized Cox proportional-hazards models. <h3>Results:</h3> The n=2240 participants had an average age of 75.5 years (SD 2.8). 52.7% were female. 36.7% were Black and 63.3% were White. Impaired odor identification (HR=2.29, 95% CI=1.79-2.94, p&lt;0.001) and global cognition (HR=3.31, 95% CI=2.26-4.84, p&lt;0.001) were each independently associated with transition to dementia (n=281). Odor identification remained robustly associated with transition to dementia for Black (HR=2.02, 95% CI=1.36-3.00, p&lt;0.001, n=821) and White participants (HR=2.45, 95% CI=1.77-3.38, p&lt;0.001, n=1419), whereas global cognition was associated with transition among Black participants only (HR=5.06, 95% CI=3.18-8.07, p&lt;0.001). ApoE genotype was consistently associated with transition among White participants only (HR=1.75, 95% CI=1.20-2.54, p&lt;0.01). Among participants with intact performance on both odor identification (BSIT ≥9/12 correct) and global cognition (3MS ≥78/100 correct), 8.8% transitioned to dementia over 8 years. Intact performance on both measures had high positive predictive value for identifying individuals who did not transition to dementia over 4 years (0.98 for ages 70-75 with only 2.3% transitioning, 0.94 for ages 76-82 with only 5.8% transitioning). <h3>Discussion:</h3> Odor identification testing paired with a global cognitive screening test identified individuals at low risk for transition to dementia in a biracial community cohort with a pronounced effect in the eighth decade of life. Identification of such individuals can reduce the need for extensive investigation to establish a diagnosis. Odor identification deficits showed utility in both Black and White participants, unlike the race-dependent utility of a global cognitive test and ApoE genotype.

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