Small-area based smoothing method for cancer risk mapping.

Lay people and health professionals are increasingly interested in health issues in their region. The high-quality cancer and population registries in the Nordic countries allow fine spatial and temporal visualization of mapped data. This article describes - with real-data examples - a mapping method developed in Finland for such visualization but also utilized for data from numerous other countries and non-cancer outcomes. The Finnish smoothing is based on weighting small-area specific observations with population sizes and distance without losing the interpretability of the values. The approach has essentially improved the readability of spatio-temporal trends of incidence and mortality rates of cancers and has been applied in many studies. With help of the tool, decision makers can understand the key message of existing data and use it more effectively in their efforts to provide better health care services.