Long-term exposure to low-level nitrogen dioxide and risks of neurodegenerative diseases among middle-aged and older adults in the UK

Divergent views remain regarding the health assessment of ambient nitrogen dioxide (NO₂) exposure at low-level concentrations. To fill in some gaps, this study was designed to comprehensively estimate the effects of low-level NO₂ exposure on the brain system. This study included 183 351 participants with ambient NO₂ ≤ 20 μg m⁻³ at baseline from the UK Biobank and analyzed associations of NO₂ exposure with neurodegenerative diseases and brain imaging traits through modeling. The results indicated that among populations exposed to ambient NO₂ ≤ 20 μg m⁻³, an interquartile range (4.7 μg m⁻³) increase in NO₂ exposure was associated with elevated incident risks of Alzheimer's disease (hazard ratio 1.18; 95% confidence interval 1.05, 1.32) and vascular dementia (1.25; 95% confidence interval 1.07, 1.46), respectively. The associations were also observed with specific grey matter and white matter phenotypes. The findings suggest that updating a lower limit for ambient NO₂ may yield significant benefits.