Environmental Air Pollution and Olfactory Decline in Aging

BACKGROUND: Olfactory impairment is increasingly common with older age, which may be in part explained by cumulative effects of exposure to inhaled toxins. However, population-based studies investigating the relationship between air pollution and olfactory ability are scarce. OBJECTIVES: We aimed to investigate associations between exposure to common air pollutants and longitudinal change in odor identification. METHODS: Our study of 2,468 participants ([Formula: see text]; 61.1% female), of which 1,774 participants ([Formula: see text]; 61.9% female) had at least two olfactory assessments over 12 y of follow-up from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), Stockholm, Sweden. Participants were free from cognitive impairment and neurodegenerative disease at baseline. Odor identification ability was assessed with Sniffin’ Sticks. Change in olfactory performance was estimated with linear mixed models. Exposure to two major airborne pollutants [particulate matter with aerodynamic diameter [Formula: see text] ([Formula: see text]) and nitrogen oxides ([Formula: see text])] for the 5 y preceding baseline was assessed using spatiotemporal dispersion models for outdoor levels at residential addresses. RESULTS: Participants showed significant decline in odor identification ability for each year in the study {[Formula: see text] [95% confidence interval (CI): [Formula: see text] , [Formula: see text]; [Formula: see text]]}. After adjustment for all covariates, residents of third [[Formula: see text] (95% CI: [Formula: see text] , [Formula: see text]; [Formula: see text])] and fourth [[Formula: see text] (95% CI: [Formula: see text] , [Formula: see text]; [Formula: see text])] exposure quartiles of [Formula: see text] had faster rates of olfactory decline than residents from the first quartile. Similar results were observed for the third [[Formula: see text] (95% CI: [Formula: see text] , [Formula: see text]; [Formula: see text])] and fourth [[Formula: see text] (95% CI: [Formula: see text] , [Formula: see text]; [Formula: see text]) quartiles of [Formula: see text]]. DISCUSSION: Our results suggest an association between air pollution exposure and subsequent olfactory decline. We speculate that cumulative effects of airborne pollutants on the olfactory system may be one underlying cause of olfactory impairment in aging. https://doi.org/10.1289/EHP9563