Effects of combined exposure to surrounding green, air pollution and traffic noise with non-accidental and cause-specific mortality in the Dutch national cohort

Abstract

Background: In daily life, people are exposed to multiple environmental factors that may affect health. The aim of this study was to evaluate associations of combined long-term residential exposure to surrounding green, air pollution and traffic noise with non-accidental and cause-specific mortality. Methods: We followed approximately 10.5 million adults (aged ≥30 years) living in the Netherlands from 1 January 2013 until 31 December 2018. We used Cox proportional hazard models to evaluate associations of combined exposure to residential surrounding green [including the average Normalized Difference Vegetation Index (NDVI) in buffers of 300m and 1000m], annual average air pollutant concentrations [including particulate matter (PM2.5), nitrogen dioxide (NO2)] and traffic noise with non-accidental and cause-specific mortality, adjusting for potential confounders. Results: In single-exposure models, surrounding green was associated with reduced risk of dying from several causes, while air pollution was associated with increased risk of dying from several causes. In two-exposure models, associations of air pollutants with non-accidental and circulatory disease mortality became weak (HR<1.015 per IQR increase), while associations of surrounding green remained. Associations of surrounding green and air pollution with respiratory disease, lung cancer and dementia mortality attenuated but generally remained in two-exposure models. For example, for dementia mortality, the HR of NO2 attenuated from 1.045 (95% CI: 1.024, 1.067) to 1.028 (95% CI: 1.006, 1.051) per IQR increase and the HR of NDVI 300m attenuated from 0.963 (95% CI: 0.950, 0.977) to 0.974 (95% CI: 0.960, 0.989) per IQR increase in a two-exposure model. Road-traffic noise was only positively associated with lung cancer mortality, also after adjustment for air pollution or surrounding green. Conclusion: Surrounding green (inversely) and air pollution (positively) were associated with non-accidental and cause-specific mortality in the Dutch national cohort. Studies including only one of these correlated exposures may overestimate the associations with mortality.