Nitrogen dioxide pollution exposure is associated with olfactory dysfunction in older US adults

Abstract

Background

Olfactory dysfunction has profound effects on quality of life, physical and social function, and mortality itself. Nitrogen dioxide (NO ₂) is a pervasive air pollutant that is associated with respiratory diseases. Given the olfactory nerve’s anatomic exposure to airborne pollutants, we investigated the relationship between NO ₂ exposure and olfactory dysfunction.

Methods

The ability to identify odors was evaluated using a validated test in respondents from the National Social Life, Health, and Aging Project (NSHAP), a representative probability sample of home-dwelling, older US adults ages 57–85. Exposure to NO ₂ pollution was assessed using measurements obtained from the US EPA AIRS ambient monitoring site closest to each respondent’s home. We tested the association between NO ₂ exposure and olfactory dysfunction using multivariate logistic regression.

Results

Among older adults in the US, 22.6% had impaired olfactory function, defined as ≤ 3 correct (out of 5) on the odor identification test. Median NO ₂ exposure during the 365 days prior to the interview date was 14.7 ppb (interquartile range [IQR] 10.8–19.7 ppb). An IQR increase in NO ₂ exposure was associated with increased odds of olfactory dysfunction (OR 1.35, 95% CI: 1.07–1.72), adjusting for age, gender, race/ethnicity, education, cognition, comorbidity, smoking, and season of the home interview (n=1,823).

Conclusion

We show for the first time that NO ₂ exposure is associated with olfactory dysfunction in older US adults. These results suggest an important role for NO ₂ exposure on olfactory dysfunction, and, potentially, nasal disease more broadly.