Protecting health data privacy while using residence-based environment and demographic data.

Spatial analyses of environment and health data are often made using point address data, despite the risk of identity disclosure. We describe how geospatial environment and non-spatial health data can be linked anonymously, thereby maintaining geoprivacy. High resolution environment data and population density were calculated specific to each residence. Population density and environment data were anonymously linked to individual-level demographic data using a split file method and residential anonymous linking fields. Access to the nearest park or playground was calculated for each residence; children in deprived areas have increased access compared to those in affluent areas. This method has the potential to be used to evaluate natural experiments and complex environmental health interventions.