The impact of monthly air pollution exposure and its interaction with individual factors: Insight from a large cohort study of comprehensive hospitalizations in Guangzhou area

BACKGROUND: Although the association between short-term air pollution exposure and certain hospitalizations has been well documented, evidence on the effect of longer-term (e. g., monthly) air pollution on a comprehensive set of outcomes is still limited. METHOD: A total of 68,416 people in South China were enrolled and followed up during 2019–2020. Monthly air pollution level was estimated using a validated ordinary Kriging method and assigned to individuals. Time-dependent Cox models were developed to estimate the relationship between monthly PM(10) and O(3) exposures and the all-cause and cause-specific hospitalizations after adjusting for confounders. The interaction between air pollution and individual factors was also investigated. RESULTS: Overall, each 10 μg/m(3) increase in PM(10) concentration was associated with a 3.1% (95%CI: 1.3%−4.9%) increment in the risk of all-cause hospitalization. The estimate was even greater following O(3) exposure (6.8%, 5.5%−8.2%). Furthermore, each 10 μg/m(3) increase in PM(10) was associated with a 2.3%-9.1% elevation in all the cause-specific hospitalizations except for those related to respiratory and digestive diseases. The same increment in O(3) was relevant to a 4.7%−22.8% elevation in the risk except for respiratory diseases. Additionally, the older individuals tended to be more vulnerable to PM(10) exposure (P(interaction): 0.002), while the alcohol abused and those with an abnormal BMI were more vulnerable to the impact of O(3) (P(interaction): 0.052 and 0.011). However, the heavy smokers were less vulnerable to O(3) exposure (P(interaction): 0.032). CONCLUSION: We provide comprehensive evidence on the hospitalization hazard of monthly PM(10) and O(3) exposure and their interaction with individual factors.