Long-term Occupational Exhaust Fumes Exposure and Delayed Cognitive Impairment in Older Adults: A Cross-sectional Study in U.S.

Abstract

Background: Occupational exposure to exhaust fumes, containing neurotoxic particulate matter and polycyclic aromatic hydrocarbons (PAHs), is associated with cardiopulmonary diseases, but its cognitive effects in aging workers remain insufficiently studied. Given increasing occupational longevity, understanding these risks is critical for dementia prevention. Methods: We analyzed data from 1,110 adults aged 60 years and older in the 2011 to 2012 National Health and Nutrition Examination Survey (NHANES), comparing cognitive performance between exposed (24%) and unexposed groups. Cognitive function was assessed using the Consortium to Establish a Registry for Alzheimers Disease Word List Learning Test (CERAD WL), Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST). Distributed lag nonlinear models (DLNMs) evaluated nonlinear and time lagged effects of exposure duration. Results: Exposed workers were predominantly male (81.6% vs. 41.8%), had lower educational attainment (31.2% vs. 24.4% with less than high school education), and exhibited higher rates of smoking (65.0% vs. 48.6%) and excessive alcohol use (15.7% vs. 7.0%). Occupational exposure was associated with significant cognitive impairments in delayed memory (odds ratio [OR] = 2.55, 95% confidence interval [CI]: 1.61 4.05), verbal fluency (OR 2.41, 1.48 3.94), and processing speed (OR 1.95, 1.19 3.18). The DLNM analyses revealed a biphasic response: minimal effects at <20 years of exposure, but major declines after 30 years, with a 15 to 25 years latency period. Conclusion: Prolonged occupational exhaust fume exposure is associated with domain specific cognitive decline, particularly affecting memory and executive function. The dose response relationship underscores cumulative neurotoxicity, emphasizing the need for targeted protections for high-exposure workers.