Another interesting finding was the significant effect modification in the association between EAD and ambient SPM by the severity of the medical condition. More specifically, our results showed that SPM was significantly associated with increased EAD only for patients with moderate
and mild medical conditions, but not with severe (i.e. serious, critical and fatal) medical conditions. To the best of our knowledge, this study is the first to focus on how different levels of illness severity can modify this association.