Implications of Mortality Displacement for Effect Modification and Selection Bias

Mortality displacement is the concept that deaths are moved forward in time (e.g., a few days, several months, and years) by exposure from when they would occur without exposure, which common environmental time-series studies. Using concepts of frail population loss life expectancy, it understood mortality may decrease rate ratio (RR). Such decreases thought to be minimal or substantial depending on study populations. Environmental epidemiologists have interpreted RR considering displacement. This theoretical paper reveals can formulated as built-in selection bias Cox models due unmeasured risk factors independent interest, also viewed an effect modifier integrating expectancy. Thus, framework through we view bias, categorized taxonomy epidemiology, simultaneously seen modifier. dichotomy provides useful implications regarding policy, modification, time-windows selection, generalizability, specifically why research epidemiology produce unexpected heterogeneous over different studies sub-populations. Keywords: Selection Effect Mediation, Directed Acyclic Graph, Frailty, Depletion susceptible, Non-collapsibility, Generalizability, Hazard (HR), Rate Ratio (RR),