Mediation and Interaction with Application to Survival After Myocardial Infarction

Sammanfattning: Previous studies have found that the socioeconomic risk factors education, income and family type were independently associated with mortality after first myocardial infarction (MI). In this population-based cohort study we study how these socioeconomic risk factors are related to the mortality among first MI survivors within 365 days. To this end, we use the four-way decomposition analysis which decomposes the total effect of the exposure into the effect that is due to only mediation, due to only interaction, due to both mediation and interaction and due to neither mediation nor interaction. Using education as exposure and income or family type as mediator two different models are estimated (adjusted for gender, age, region of birth and year of admission). For the model in which income was used as mediator, results show that individuals with lower education and a lower income are at greater risk of mortality, compared to individuals with the highest income level. The mediated effect of income on mortality decreases as the income approaches the highest income. In the model with family type as mediator the mediated effect on mortality was found to be low, meanwhile the direct effect of lower education was most substantial to the total risk of mortality.