syndemic approach to the study of Covid-19-related death: a cohort study using UK Biobank data.

BACKGROUND: The Covid-19 pandemic showed higher infection, severity and death rates among those living in poorer socioeconomic conditions. We use syndemic theory to guide the analyses to investigate the impact of social adversity and multiple long-term conditions (MLTC) on Covid-19 mortality. METHODS: The study sample comprised 154 725 UK Biobank participants. Structural equation modeling was used to investigate pathways between traumatic events, economic deprivation, unhealthy behaviors, MLTC, for Covid-19 mortality. Cox regression analysis was used to investigate MLTC and Covid-19 mortality. We also tested effect modification by traumatic events, economic deprivation and unhealthy behaviors. RESULTS: Covid-19 mortality (n = 186) was directly explained by overall level of MLTC. Economic deprivation and unhealthy behaviors contributed to Covid-19 death indirectly via their negative impact on MLTC. The risk for Covid-19 mortality grew exponentially for every quintile of predicted scores of MLTC. The presence of traumatic events, economic deprivation or unhealthy behaviors did not modify the impact of MLTC on Covid-19 mortality. CONCLUSIONS: Results suggest a serially causal pathway between economic deprivation and unhealthy behaviors leading to MLTC, which increased the risk of Covid-19 mortality. Policies to tackle the social determinants of health and to mitigate the negative impact of multimorbidity are needed.