Exposure to Particulate Matter Air Pollution and Anosmia

Importance: Anosmia, the loss of the sense of smell, has profound implications for patient safety, well-being, and quality of life, and it is a predictor of patient frailty and mortality. Exposure to air pollution may be an olfactory insult that contributes to the development of anosmia. Objective: To investigate the association between long-term exposure to particulate matter (PM) with an aerodynamic diameter of no more than 2.5 μm (PM_2.5) with anosmia. Design, Setting, and Participants: This case-control study examined individuals who presented from January 1, 2013, through December 31, 2016, at an academic medical center in Baltimore, Maryland. Case participants were diagnosed with anosmia by board-certified otolaryngologists. Control participants were selected using the nearest neighbor matching strategy for age, sex, race/ethnicity, and date of diagnosis. Data analysis was conducted from September 2020 to March 2021. Exposures: Ambient PM_2.5levels. Main Outcomes and Measures: Novel method to quantify ambient PM_2.5exposure levels in patients diagnosed with anosmia compared with matched control participants. Results: A total of 2690 patients were identified with a mean (SD) age of 55.3 (16.6) years. The case group included 538 patients with anosmia (20%), and the control group included 2152 matched control participants (80%). Most of the individuals in the case and control groups were women, White patients, had overweight (BMI 25 to <30), and did not smoke (women: 339 [63.0%] and 1355 [63.0%]; White patients: 318 [59.1%] and 1343 [62.4%]; had overweight: 179 [33.3%] and 653 [30.3%]; and did not smoke: 328 [61.0%] and 1248 [58.0%]). Mean (SD) exposure to PM_2.5was significantly higher in patients with anosmia compared with healthy control participants at 12-, 24-, 36-, 60-month time points: 10.2 (1.6) μg/m³vs 9.9 (1.9) μg/m³; 10.5 (1.7) μg/m³vs 10.2 (1.9) μg/m³; 10.8 (1.8) μg/m³vs 10.4 (2.0) μg/m³; and 11.0 (1.8) μg/m³vs 10.7 (2.1) μg/m³, respectively. There was an association between elevated PM_2.5exposure level and odds of anosmia in multivariate analyses that adjusted for age, sex, race/ethnicity, body mass index, alcohol or tobacco use, and medical comorbidities (12 mo: odds ratio [OR], 1.73; 95% CI, 1.28-2.33; 24 mo: OR, 1.72; 95% CI, 1.30-2.29; 36 mo: OR, 1.69; 95% CI, 1.30-2.19; and 60 mo: OR, 1.59; 95% CI, 1.22-2.08). The association between long-term exposure to PM_2.5and the odds of developing anosmia was nonlinear, as indicated by spline analysis. For example, for 12 months of exposure to PM_2.5, the odds of developing anosmia at 6.0 µg/m³was OR 0.79 (95% CI, 0.64-0.97); at 10.0 µg/m³, OR 1.42 (95% CI, 1.10-1.82); at 15.0 µg/m³, OR 2.03 (95% CI, 1.15-3.58). Conclusions and Relevance: In this study, long-term airborne exposure to PM_2.5was associated with anosmia. Ambient PM_2.5represents a potentially ubiquitous and modifiable risk factor for the loss of sense of smell.