Long-Term Exposure to Air Pollution and Road Traffic Noise and Incidence of Chronic Obstructive Pulmonary Disease: The Danish Nurse Cohort

Abstract

Background: While air pollution has been linked to the development of chronic obstructive pulmonary disease (COPD), evidence on the role of environmental noise is just emerging. We examined the association of long-term exposure to air pollution and road traffic noise with COPD incidence. Methods: We defined COPD incidence for 24,538 female nurses from the Danish Nurse Cohort (age > 44 years) as the first hospital contact between baseline (1993 or 1999) and 2015. We estimated residential annual mean concentrations of particulate matter with diameter < 2·5 µm (PM2·5) since 1990 and nitrogen dioxide (NO2) since 1970 by the Danish DEHM/UBM/AirGIS modeling system, and road traffic noise (Lden) since 1970 by the Nord2000 model. Time-varying Cox regression models were applied to assess the associations of air pollution and noise with COPD incidence. Findings: 977 nurses developed COPD during 18·6 years’ mean follow-up. We observed associations with COPD for all three exposures with hazard ratios (HRs) and 95% confidence intervals (CIs) of 1·19 (1·01, 1·41) per 6·26 µg/m3 for PM2·5, 1·13 (1·05, 1·20) per 8·19 µg/m3 for NO2, and 1·15 (1·06, 1·25) per 10 dB for Lden. Associations with NO2 and Lden attenuated slightly after adjustment for each other, but were robust to adjustment for PM2·5. Associations with PM2·5 were attenuated to null after adjustment for either NO2 or Lden. Interpretation: Long-term exposures to traffic-related NO2 and road traffic noise were associated with COPD, independent of each other. Funding Statement: Danish Council for Independent Research, Novo Nordisk Foundation, and China Scholarship Council. Funding Statement: This work was supported by the Danish Council for Independent Research [DFF-4183-00353], the Novo Nordisk Foundation Challenge Programme [NNF17OC0027812], and the China Scholarship Council [No. 201806010406]. Declaration of Interests: We declare that we have no conflicts of interest. Ethics Approval Statement: The establishment of the cohort was approved by the Scientific and Ethical Committee of Copenhagen and Frederiksberg Municipalities, and the Danish Data Protection Agency.