The impact of air pollution on influenza incidence in high-altitude regions: a time-stratified case-crossover study based on Qinghai Province.

Background: The unique characteristics of air pollution in high-altitude regions may significantly influence the transmission and incidence of influenza. However, current research on this phenomenon is limited, and further investigation is urgently needed.

Methods: This study collected influenza outpatient data from Qinghai Province between January 1, 2016, and December 31, 2021. We employed a time-stratified case-crossover design combined with conditional Poisson regression models to quantitatively analyze the relationship between air pollutants (PM_2.5, SO₂, NO₂) and influenza incidence and explored the moderating role of temperature in this relationship. Additionally, stratified analyses were conducted to identify potential vulnerable populations.

Results: The study results indicated that exposure to PM_2.5, SO₂, and NO₂ was positively associated with the risk of influenza incidence. For every 10 µg/m³ increase in the concentration of PM_2.5, SO₂, and NO₂, the percentage change in relative risk (RR) of influenza incidence was 0.35% (95% CI: 0.02%, 0.68%), 2.24% (95% CI: 1.42%, 3.06%), and 1.91% (95% CI: 1.16%, 2.67%), respectively. Under low-temperature conditions, the impact of pollutants other than O₃ on influenza incidence was particularly pronounced. Children, the elderly, and individuals living at altitudes of 3000-3500 m were more sensitive to these pollutants.

Conclusion: This study revealed a close link between air pollution and influenza in high-altitude regions, with greater health risks under low-temperature conditions. The findings underscore the necessity of strengthening air quality monitoring and raising public awareness of environmental health.