Seasonal impact of air particulate matter on morbidity: Interaction effect assessment in a time-stratified case-crossover design

Abstract

The present study aimed to explore the interaction effect between PM₁₀ and season as well as temperature on hospital admissions (HAs) in a region in North East of Iran. Distributed lag non-linear model in a time-stratified case-crossover design with a fixed and disjointed window was used in order to assess the impact of PM₁₀ on HAs. Two approaches were applied to assess the interaction effect between season and the pollutant named stratification and interaction term in the regression model. In addition, a bivariate response surface model in Generalized Additive Model (GAM) was used to explore the interaction effect between PM₁₀ and weather parameters, in order to see whether the seasonal variation of the PM₁₀ effect is explained by weather conditions or not. The existence of interaction effect between PM₁₀ and season was supported by both approaches; it was evident that spring significantly shared a large proportion of the adverse impact of PM₁₀ on HAs. However, the interactive effects of PM₁₀ and mean temperature were less obvious in this study. The results showed that all people were at risk of HAs due to high levels of PM₁₀, with a particularly more immediate impact on elderlies. The results of the interaction effect can help policymakers to address spring when any preventive interventions are developed in the region.

Keywords:

• PM₁₀
• hospital admissions
• season
• interaction effect

Acknowledgements

The authors thank the Deputy of Health of North Khorasan University of Medical Sciences for providing the data.

Disclosure statement

No potential conflict of interest was reported by the authors.

Ethics approval

The proposal for this study was approved by the Ethics Committee of North Khorasan University of Medical Sciences. Ethics code is IR.NKUMS.REC.1400.032

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by the Deputy of research and technology, North Khorasan University of Medical Sciences (Grant No. 990175).