Individual participant data meta-analysis of cohort studies to investigate the health effects of long-term exposure to air pollution: A multi-center study

It is estimated that 6.6 million (11.8%) deaths were attributed to air pollution worldwide in 2019, and the majority (6.5 million) were due to particulate matter pollution. Studies have documented that air pollution was linked to various circulatory and respiratory diseases and premature mortality. Previous studies mainly examined short-term exposure to air pollution, while few cohort studies examined the effects of long-term exposure to air pollution. Long-term exposure may exert long-standing, irreversible and larger effects on human health in comparison, resulting in a much greater disease burden. Additionally, most of the studies were based on one regional cohort and thus the results were reflections of the specific region/country, making it difficult to generalize findings to different ethnic contexts with different exposure levels. 
Therefore, this project aims to pool data from the representative large cohorts from Asia, America and Europe to determine the concentration-response associations between long-term exposure to air pollution (PM2.5, NO2, and O3) and the risk of morbidity and mortality. In addition, we aim to analyze the potential effect modifications by age, sex, ethnicity, lifestyles, socio-economic factors, and pre-existing diseases and explore the potential mechanisms for the heterogeneity of the air pollution-health associations across different populations.