Spatial variability in mortality inequalities, socioeconomic deprivation, and air pollution in small areas of the Barcelona Metropolitan Region, Spain.

Background: There is evidence that geographic variability of social health inequalities continues to exist even after individual risk factors have been taken into account. However, relatively few studies have examined the contribution of exposure to air pollutants to those inequalities.
Objectives: To study the geographic variability of inequalities in mortality and their associations with socioeconomic and environmental inequalities in small areas of the metropolitan of Barcelona during the period 1994 to 2003.
Methods: As in the MEDEA Project, the small area unit was the census tract. Study population consisted of the residents of the metropolitan area of Barcelona. Response variables were all-cause and specific-cause standardized mortality ratio (SMR). Explanatory variables were deprivation index, summarizing socioeconomic variables of the census tracts, and estimates of air pollutant exposures. Bayesian hierarchical models were used in order to reduce the extra variability when using SMR and to assess associations between mortality and deprivation and air pollution.
Results: Statistically significant associations with deprivation were found for the causes of death related to consumption of tobacco and alcohol for men and, besides lung cancer, diet-related causes for women. Statistically significant pollution coefficients were only found in the metropolitan area of Barcelona and in men. A positive interaction between pollutants and the deprivation index was statistically significant for respiratory mortality and PM(10), and ischemic disease mortality and NO(2), both for men.
Conclusions: We found deprivation to be associated in a statistically significant way with the geographical variation in mortality in the census tracts of the metropolitan area of Barcelona, in the period 1994 to 2003. Those air pollutants more directly related with traffic modify some of these associations.