Fig. 1

Causal graph. The variables are considered at the departmental scale. The effect of X on Y can be estimated by adjusting on {Diab., Age, Beds}. X: COVID-19 incidence. Y: IFR (infection fatality rate) or IHR (infection hospitalization rate). Diab.: Prevalence of diabetes. Beds: Number of intensive care beds per inhabitant. Age: Proportion of population over 60. Dashed arrows represent the effects of unmeasured confounders C.