The association between air pollutants and mild cognitive impairment in Taiwanese elderly

Mild cognitive impairment (MCI) is considered a prodromal stage of dementia, and cognitive decline is generally challenging to reverse. Recently, air pollution has been identified as a risk factor for cognitive impairment, making the exploration of this association an essential research topic. However, nationwide studies investigating the relationship between air pollution and MCI are still lacking.

This study aimed to investigate the association between air pollution and MCI in Taiwan.

This cross-sectional study utilized data from the Taiwan Biobank, retrieved elderly participants aged above 60, between 2008 and 2021. The study collected demographic data and cognitive function assessments using the Mini-Mental State Examination (MMSE) scale. MCI was defined by cut-off scores of 18, 21, and 25 according to educational levels. Google Map was used to locate the nearest air quality monitoring station from the residential address of participants. Individual daily average exposure concentrations of PM_2.5, PM₁₀, SO₂, O₃, CO, and NO₂ were sourced from the air quality monitoring station of Environmental Protection Administration (EPA) between 1993 and 2021. Regression models were employed to identify factors associated with MCI in Taiwan.

This study contains 4,173 cases with MCI and 31,022 controls, representing an MCI prevalence of 11.9%. The individual daily average exposure concentrations of PM_2.5, PM₁₀, O₃, CO, SO₂ and NO₂ are 30.70±8.38 μg/m³, 59.25±15.81 μg/m³, 25.96±3.08 ppb, 0.65±0.42 ppm, 4.97±2.59 ppb and 20.22±5.09 ppb, respectively. Tertiles of pollution exposure in regression models show that higher exposure to PM_2.5 and SO₂ are associated with a higher risk of MCI compared to that of lower exposure levels (OR = 1.23, 95% CI: 1.11-1.37; OR = 1.20, 95% CI: 1.07-1.34). Furthermore, concurrent exposure to the highest tertiles (T3) of both PM_2.5 and SO₂ increased the risk of MCI to 2.33 (95% CI: 1.56-3.48).

We found evidence of the effect of PM_2.5 and SO₂ on MCI among elderly individuals in Taiwan. Moreover, the association between PM_2.5 and MCI risk escalated with higher SO₂ concentrations, demonstrating a synergistic interaction between the two pollutants. This discovery may provide evidence for policy of MCI prevention.