Study data published in JAMA Neurology suggest that ambient air pollution may be associated with amyloid-β (Aβ) deposition in older adults with cognitive impairment. In a cross-sectional analysis, older adults living in areas with high concentrations of fine particulate matter (PM2.5) were more likely to receive a positive result from an amyloid Positron Emission Tomography (PET) scan than older adults living in areas with lower PM2.5 pollution.

Investigators extracted data from the Imaging Dementia—Evidence for Amyloid Scanning Study, which comprises data from more than 18,000 adults in the United States with cognitive impairment who received an amyloid PET scan between February 16, 2016 and January 10, 2018. Eligible PET scans used 1 of 3 radiopharmaceutical Aβ tracers: fluorine 18 [18F]–labeled florbetapir, 18F-labeled florbetaben, or 18F-labeled flutemetamol. Data from the United States Environmental Protection Agency Downscaler model were used to estimate PM2.5 and ground-level ozone (O3) concentrations at each patient’s area of residence.

Air quality was calculated for 2 periods prior to amyloid PET scans: 2002-2003 (13-15 years before scan) and 2015-2016 (0-2 years before scan). Logistic regression was used to assess the relationship between exposure to air pollution and the likelihood of amyloid PET scan positivity. Models were adjusted for demographic and clinical characteristics, including comorbid medical conditions.

The study cohort included 18,178 patients, among whom 10,991 (60.5%) had mild cognitive impairment (MCI) and 7,187 (39.5%) had dementia. Mean age was 75.8 ± 6.3 years, and 51.3% of participants were women. Living in areas with higher estimated PM2.5 concentrations during 2002-2003 was associated with increased odds of amyloid PET scan positivity (odds ratio [OR], 1.10; 95% CI, 1.05-1.15).


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For each 1 μg/m3 increase in PM2.5 for the 2002-2003 period, the probability of amyloid PET scan positivity increased by an average marginal effect (AME) of 0.5%. Increased PM2.5 exposure during 2015-2016 was also associated with amyloid PET scan positivity (OR, 1.15; 95% CI, 1.05-1.26). In this period, the AME was +0.8% for each 1 μg/m3 increase in PM2.5. The relationship between air pollution and PET scan positivity did not appear to be affected by patient sex or clinical stage of cognitive impairment. Exposure to higher O3 concentrations was not associated with PET scan positivity during either time period.

This study builds on prior research suggesting a link between polluted air and Aβ production and deposition. As a study limitation, investigators noted that air pollution exposure was estimated based on address of residence. Occupational exposure could not be estimated, nor could each patient’s average exposure to outdoor air. Future research is necessary to better understand the relationship between airborne pollutants and cognitive impairment.

“These findings suggest the need to consider airborne toxic pollutants associated with Aβ pathology in public health policy decisions and to inform individual lifetime risk of developing AD and dementia,” the investigators wrote.

Disclosure: Two study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Iaccarino L, La Joie R, Lesman-Segev OH, et al. Association between ambient air pollution and amyloid positron emission tomography positivity in older adults with cognitive impairment. JAMA Neurol. Published online November 30, 2020. doi:10.1001/jamaneurol.2020.3962