Long-term exposure to pollutants — black carbon (BC), nitrogen dioxide (NO2), and/or fine particulate matter (PM2.5) — was associated with death in asthma, dementia, psychiatric disorders, diabetes, and acute lower respiratory infection, as well as cardiorespiratory diseases, according to Danish study findings published recently in Environmental International.

Previous studies link air pollution with cardiovascular, respiratory, and lung cancer disease deaths, and recent studies suggest connections between air pollution and stroke, type-2 diabetes, and adverse birth outcomes. Researchers for the current study sought to investigate the association between long-term air-pollution exposure and natural-cause death as well as death related to multiple diseases/conditions.

The researchers conducted a retrospective administrative cohort study of all residents in Denmark older than 29 years of age (3,083,227) from January 2000 through December 2017. The primary study endpoint was death due to all-natural cause mortality, cardiovascular disease, respiratory disease, lung cancer, diabetes, dementia, psychiatric disorders other than dementia, asthma, acute lower respiratory infection (ALRI), and chronic kidney disease (CKD). European-wide hybrid land-use regression models were utilized to estimate annual mean concentrations of BC, NO2, and PM2.5. The association between air pollution and death was evaluated with Cox proportional hazard models.


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During more than 47 million person-years of follow-up, 803,881 people died from natural causes in Denmark. All of the studied mortality outcomes were significantly associated with long-term exposure to BC, NO2, and PM2.5 except CKD. An increase in PM2.5 of 5 μg/m3 was associated with higher death rates from all-natural causes (hazard ratio [HR] 1.11; 95% CI, 1.09-1.13), cardiovascular disease (HR 1.09; 95% CI, 1.07-1.12), respiratory disease (HR 1.11; 95% CI, 1.07-1.15), lung cancer (HR 1.19; 95% CI, 1.15-1.24), diabetes (HR 1.10; 95% CI, 1.04-1.16), dementia (HR 1.05; 95% CI, 1.00-1.10), psychiatric disorders (HR 1.38; 95% CI, 1.27-1.50), asthma (HR 1.13; 95% CI, 0.94-1.36), and ALRI (HR 1.14; 95% CI, 1.09-1.20). Long-term ozone exposure did not show associations except in 2-pollutant models. Indirect statistical adjustment for smoking and BMI attenuated associations but not below the level of significance.

Researchers concluded that “In the large nationwide administrative cohort of over 3 million Danish adult residents, long-term exposure to PM2.5, NO2, and BC was associated with increased risk of mortality from diabetes, dementia, and psychiatric disorders as well as mortality from all-natural causes, CVD, RD, and lung cancer.”

Study limitations included missing information on additional air pollution exposure, unaccounted for effect of road-traffic noise associated with the effect of air pollution, exposure misclassification, unaccounted for temporal variation, and missing information on lifestyle.

Disclosure: This research was supported by Novo Nordisk. Please see the original reference for a full list of disclosures.

Reference

So R, Andersen ZJ, Chen J, et al. Long-term exposure to air pollution and mortality in a Danish nationwide administrative cohort study: Beyond mortality from cardiopulmonary disease and lung cancer. Environ Int. Published online April 12, 2022. doi:10.1016/j.envint.2022.107241