BACKGROUND: The effect of air pollution on annual change rates in grip strength and body composition in the elderly is unknown. OBJECTIVES: This study evaluated the effects of long-term exposure to ambient air pollution on change rates of grip strength and body composition in the elderly. METHODS: In the period 2016-2020, grip strength and body composition were assessed and measured 1-2 times per year in 395 elderly participants living in the Taipei basin. Exposure to ambient fine particulate matters (PM_2.5), nitric dioxide (NO₂), and ozone (O₃) from 2015 to 2019 was estimated using a hybrid Kriging/Land-use regression model. In addition, long-term exposure to carbon monoxide (CO) was estimated using an ordinary Kriging approach. Associations between air pollution exposures and annual changes in health outcomes were analyzed using linear mixed-effects models. RESULTS: An inter-quartile range (4.1 µg/m³) increase in long-term exposure to PM_2.5 was associated with a faster decline rate in grip strength (-0.16 kg per year) and skeletal muscle mass (-0.14 kg per year), but an increase in body fat mass (0.21 kg per year). The effect of PM_2.5 remained robust after adjustment for NO₂, O₃ and CO exposure. In subgroup analysis, the PM_2.5-related decline rate in grip strength was greater in participants with older age (>70 years) or higher protein intake, whereas in skeletal muscle mass, the decline rate was more pronounced in participants having a lower frequency of moderate or strenuous exercise. The PM_2.5-related increase rate in body fat mass was higher in participants having a lower frequency of strenuous exercise or soybean intake. CONCLUSIONS Among the elderly, long-term exposure to ambient PM_2.5 is associated with a faster decline in grip strength and skeletal muscle mass, and an increase in body fat mass. Susceptibility to PM_2.5 may be influenced by age, physical activity, and dietary protein intake; however, these modifying effects vary across different health outcomes, and further research is needed to clarify their mechanisms and consistency.
Humans ; Hand Strength ; Aged ; Male ; Female ; Environmental Exposure/adverse effects* ; Follow-Up Studies ; Taiwan ; Air Pollution/adverse effects* ; Particulate Matter/adverse effects* ; Muscle, Skeletal/drug effects* ; Air Pollutants/adverse effects* ; Ozone/adverse effects* ; Aged, 80 and over ; Adipose Tissue/drug effects* ; Body Composition/drug effects* ; Nitrogen Dioxide/adverse effects*

BACKGROUND: Metabolic Dysfunction-associated Steatotic Liver Disease (MASLD) has become a global epidemic, and air pollution has been identified as a potential risk factor. This study aims to investigate the non-linear relationship between ambient air pollution and MASLD prevalence. METHOD: In this cross-sectional study, participants undergoing health checkups were assessed for three-year average air pollution exposure. MASLD diagnosis required hepatic steatosis with at least 1 out of 5 cardiometabolic criteria. A stepwise approach combining data visualization and regression modeling was used to determine the most appropriate link function between each of the six air pollutants and MASLD. A covariate-adjusted six-pollutant model was constructed accordingly. RESULTS: A total of 131,592 participants were included, with 40.6% met the criteria of MASLD. "Threshold link function," "interaction link function," and "restricted cubic spline (RCS) link functions" best-fitted associations between MASLD and PM_2.5, PM₁₀/CO, and O₃ /SO₂/NO₂, respectively. In the six-pollutant model, significant positive associations were observed when pollutant concentrations were over: 34.64 µg/m³ for PM_2.5, 57.93 µg/m³ for PM₁₀, 56 µg/m³ for O₃, below 643.6 µg/m³ for CO, and within 33 and 48 µg/m³ for NO₂. The six-pollutant model using these best-fitted link functions demonstrated superior model fitting compared to exposure-categorized model or linear link function model assuming proportionality of odds. CONCLUSION Non-linear associations were found between air pollutants and MASLD prevalence. PM_2.5, PM₁₀, O₃, CO, and NO₂ exhibited positive associations with MASLD in specific concentration ranges, highlighting the need to consider non-linear relationships in assessing the impact of air pollution on MASLD.
Humans ; Nitrogen Dioxide ; Cross-Sectional Studies ; Air Pollution/analysis* ; Air Pollutants/analysis* ; Particulate Matter/analysis* ; Liver Diseases ; Environmental Exposure/analysis*