The development of a measure of multiple physical environmental deprivation for epidemiological research. After United Kingdom and New Zealand, Portugal

Introduction: Spatial inequalities in health have been identified throughout the world. Diverse multivariate deprivation indexes have been developed to explain such inequalities. Most indexes are based on socioeconomic characteristics and physical environment has been all but ignored. This is surprising, given the contribution of physical environment to mortality and morbidity. Based on previous United Kingdom (UK) and New Zealand (NZ) research, which created a Multiple Environmental Deprivation Index (MEDIx), we developed a Portuguese version – PT-MEDIx.

Methods: PT-MEDIx was built at municipality-level (n=278, average population=35,000 inhabitants). The approach followed five stages: 1) identify health-relevant environmental factors, based on an extensive literature review; 2) acquire datasets about selected environmental factors and calculate municipality-level measures using Geographical Information Systems; 3) test associations between selected environmental factors and mortality using negative binomial models, adjusting for age, sex and socioeconomic deprivation; 4) construct a summary measure (PT-MEDIx) and 5) assess its association with mortality.

Results: We selected four dimensions of the physical environment: air pollution (particulate matter, carbon monoxide and nitrogen dioxide), climate (mean temperature), drinking water quality (trihalomethanes and nitrates), green space availability & proximity to polluting industry. PT-MEDIx score ranged from -1 (least environmental deprivation) to +4 (most). The index identified a clear spatial pattern within Portugal: least environmentally deprived municipalities in the inner north and center and most deprived in urban settings. Comparing with the intermediate group (PT-MEDIx=0) there was a significant positive association between environmental deprivation and all-cause (IRR=0.980 [0.961-1.001] in the least deprived, 1.024 [1.004-1.045] in the most deprived); cardiovascular (IRR=0.942 [0.912-0.974], 1.062 [1.028-1.097]) and cancer mortality (IRR=0.944 [0.909-0.973], 1.111 [1.084-1.128]). A dose-response relationship was particularly evident for cancer mortality. 

Conclusions: Earlier UK/NZ indexes have good transferability to Southern Europe, meaning that the replication of MEDIx might contribute to untangle the complex pathways that link health, socioeconomic and physical environment.