Do socioeconomic inequalities in mortality vary between different Spanish cities? a pooled cross-sectional analysis.

ABSTRACT

BACKGROUND: The relationship between deprivation and mortality in urban settings is well established. This relationship has been found for several causes of death in Spanish cities in independent analyses (the MEDEA project). However, no joint analysis which pools the strength of this relationship across several cities has ever been undertaken. Such an analysis would determine, if appropriate, a joint relationship by linking the associations found. METHODS: A pooled cross-sectional analysis of the data from the MEDEA project has been carried out for each of the causes of death studied. Specifically, a meta-analysis has been carried out to pool the relative risks in eleven Spanish cities. Different deprivation-mortality relationships across the cities are considered in the analysis (fixed and random effects models). The size of the cities is also considered as a possible factor explaining differences between cities. RESULTS: Twenty studies have been carried out for different combinations of sex and causes of death. For nine of them (men prostate cancer, diabetes, mental illnesses, Alzheimer's disease, cerebrovascular disease; women diabetes, mental illnesses, respiratory diseases, cirrhosis) no differences were found between cities in the effect of deprivation on mortality; in four cases (men respiratory diseases, all causes of mortality; women breast cancer, Alzheimer's disease) differences not associated with the size of the city have been determined; in two cases (men cirrhosis; women lung cancer) differences strictly linked to the size of the city have been determined, and in five cases (men lung cancer, ischaemic heart disease; women ischaemic heart disease, cerebrovascular diseases, all causes of mortality) both kinds of differences have been found. Except for lung cancer in women, every significant relationship between deprivation and mortality goes in the same direction deprivation increases mortality. Variability in the relative risks across cities was found for general mortality for both sexes. CONCLUSIONS: This study provides a general overview of the relationship between deprivation and mortality for a sample of large Spanish cities combined. This joint study allows the exploration of and, if appropriate, the quantification of the variability in that relationship for the set of cities considered.