Characterizing the olfaction and dementia association in the community-based ARIC study

Abstract

Introduction: Few studies have characterized the association of olfaction with dementia in detail across diverse sociodemographic subgroups.

Methods: We examined the association of one-time-point olfactory status with incident dementia overall and by age, race, sex, and apolipoprotein E (APOE) ε4 status (n = 4470, mean age: 75 ± 5 years, 21% Black), and 5-year olfactory change with incident dementia (n = 2658) in the community-based Atherosclerosis Risk in Communities (ARIC) study.

Results: Compared to good olfaction, moderate olfaction (hazard ratio [HR]: 1.53, 95% confidence interval [CI]: 1.26 to 1.86), hyposmia (HR: 2.24, 95% CI: 1.81 to 2.78), and anosmia (HR: 3.47, 95% CI: 2.77 to 4.34) were all associated with higher dementia hazard; these associations were consistent across age, race, sex, and APOE ε4 groups. The absolute risk difference between anosmia and good olfaction was higher in APOE ε4 carriers than in non-carriers. Those with stable anosmia and converting from normal olfaction to anosmia over time showed particularly strong associations.

Discussion: Olfactory impairment was robustly associated with incident dementia, with strongest associations in those with persistent impairment and greater olfactory decline over ∼5 years.

Highlights: We examined olfactory status and olfactory change in relation to incident dementia. Poor olfactory status was robustly associated with higher dementia rate. Associations were robust across subgroups of age, sex, race, and APOE ε4 status. Persistent poor olfaction or decline over time showed the strongest associations.

Keywords: dementia; olfaction; olfactory change; prospective cohort.