Association between air pollutants and dementia risk in the elderly

Background: The aging rate in Taiwan is the second highest in the world. As the population ages quickly, the prevalence of dementia increases rapidly. There are some studies that have explored the association between air pollution and cognitive decline, but the association between air pollution and dementia has not been directly evaluated. Methods: This was a case-control study comprising 249 Alzheimer's disease (AD) patients, 125 vascular dementia (VaD) patients, and 497 controls from three teaching hospitals in northern Taiwan from 2007 to 2010. Data of particulate matter <10μm in diameter (PM₁₀) and ozone were obtained from the Taiwan Environmental Protection Administration for 12 and 14years, respectively. Blood samples were collected to determine the apolipoprotein E (APOE) ε4 haplotype. Bayesian maximum entropy was used to estimate the individual exposure level of air pollutants, which was then tertiled for analysis. Conditional logistic regression models were used to estimate adjusted odds ratios (AORs) and 95% confidence intervals between the association of PM₁₀ and ozone exposure with AD and VaD risk. Results: The highest tertile of PM₁₀ (≥49.23μg/m³) or ozone (≥21.56ppb) exposure was associated with increased AD risk (highest vs. lowest tertile of PM₁₀: AOR=4.17; highest vs. lowest tertile of ozone: AOR=2.00). Similar finding was observed for VaD. The association with AD and VaD risk remained for the highest tertile PM₁₀ exposure after stratification by APOE ε4 status and gender. Conclusions: Long-term exposure to the highest tertile of PM₁₀ or ozone was significantly associated with an increased risk of AD and VaD.