Air pollution exposure associated with decline rates in skeletal muscle mass and grip strength and increase rate in body fat in elderly: a 5-year follow-up study

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 (¹0.16 kg per year) and skeletal muscle mass (¹0.14 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.