Joint effects of air pollution and diet patterns on the risk of chronic obstructive pulmonary disease

Diet patterns and air pollution have been recognized as factors that affect the onset of chronic obstructive pulmonary disease (COPD). However, the combined effects of these factors on COPD incidence remain unclear. On the basis of a large prospective cohort from UK Biobank, we explored the independent and joint effects of diet patterns and air pollution on the risk of COPD. A total of 314,226 participants from UK Biobank, who were recruited between 2006 and 2010, were included in this study. The participants were randomly divided into the training (70%) and validation (30%) sets, with the air pollution score calculated using the training set. A diet pattern score was constructed in accordance with the intake of fruits, vegetables, fish, processed meat, unprocessed red meat, whole grains, and refined grains. Meanwhile, an air pollution score was calculated by determining the exposure levels to four components: fine particulate matter (PM2.5), PM2.5-10, NO2, and NOx. Cox proportional hazard models with hazard ratios (HRs) and 95% confidence intervals (CIs) were applied to examine the independent effects of diet patterns and air pollution on COPD incidence. Interaction analyses at the multiplicative and additive scales were also applied to assess the joint effects of diet patterns and air pollution on COPD risk. The above analyses were performed on both the training and validation datasets to verify the robustness of the results. In the training set, 6,696 participants were diagnosed with COPD during a median follow-up duration of 13.9 years. In the fully adjusted model, participants with intermediate and low diet pattern scores had higher COPD risk compared with those with high diet pattern score, with HRs being 1.11 (95% CI: 1.05 to 1.17) and 1.31 (95% CI: 1.21 to 1.42), respectively. Moreover, heavier exposure to air pollution was associated with higher COPD risk, with HRs being 1.06 (95% CI: 1.03, 1.14) and 1.13 (95% CI: 1.05, 1.22) for quintiles Q4 and Q5, respectively, compared with that for quintile Q1. Similar results were observed in the validation dataset. Analyses revealed limited evidence of significant joint effects between diet pattern and air pollution scores on either the multiplicative or additive scales, both in the training and validation sets. Targeted intervention on modifiable diet patterns may offset the adverse effect of air pollution exposure on COPD risk.