Adaptive Ecological Study — Adaptive Population-Level Observational Design

An adaptive ecological study is an observational epidemiological design in which the unit of analysis is a group or population (e.g., a region, country, or community) rather than an individual. It extends the classical ecological study by incorporating pre-specified interim decision rules that allow modifications — such as changes in geographic unit, time window, or exposure categorisation — as data accumulate, while preserving overall inferential validity. The design is used to explore population-level associations between aggregate exposures and aggregate outcomes.