Population health is influenced by many socioeconomic and demographic factors that may include levels of employment, income, education, ethnicity and age. For health planning and service delivery, it is important to take into account demographic trends over time. This temporal component is usually incorporated into analyses by comparing multiple maps of variables at different points in time. In this study demographic variables with spatial and temporal components are used in a multi-criteria analysis within an interactive spatial decision support tool. We illustrate how the exploration of an area-based composite index over time can help analysts with identifying trends of increasing social deprivation and health-care needs. The paper focuses on the conceptual challenges of spatio-temporal multi-criteria analysis due to changing geographic boundaries, the standardization of variables across time, comparability of variables, and comparability of index scores.