Effect modification of dietary diversity on the association of air pollution with incidence, complications, and mortality of type 2 diabetes: Results from a large prospective cohort study

Abstract

Background: It remains unknown whether the dietary diversity score (DDS) could modify the association of long-term exposure to individual air pollutants and the mixture of various pollutants with the incidence, complications, and mortality of type 2 diabetes (T2D).

Methods: We included 162,579 participants from the UK Biobank who had ≥ one 24-h dietary assessment and were free of diabetes or diabetes complications before their last response date of the 24-h dietary assessment. Exposure to benzene, NO_x, NO₂, SO₂, PM₁₀, and PM_2.5 was estimated at each participant's residential location using a bilinear interpolation algorithm based on air dispersion models on a 1 km × 1 km grid. The DDS was calculated based on repeated 24-h dietary assessments. The outcomes were the incidence, complications, and mortality of T2D. Associations of individual pollutants and multiple pollutants mixtures with outcomes were assessed using Cox proportional hazards regression models and the quantile g-computation approach, respectively. We further stratified these analyses by DDS.

Results: During a median of 10.1 years of follow-up, 2978 participants developed incident T2D, 1181 developed T2D complications, and 242 died due to T2D. Long-term single-pollutant and multi-pollutant exposure were associated with elevated risk of incidence, complications, and mortality of T2D. For example, for incident T2D, the hazard ratio and 95 % confidence interval for each quantile increase were 1.155 (1.095, 1.215) for the air pollution mixture. We observed significant interactions between air pollution (benzene, NO_x, NO₂, PM₁₀, PM_2.5, and the air pollution mixture) and DDS (P-interaction <0.05), with the corresponding associations being significantly weaker in adults with high DDS than in those with low DDS.

Conclusion: Higher dietary diversity may attenuate the harmful impacts of air pollution on T2D-related outcomes. A higher diversity diet could be used to prevent the onset and progression of T2D induced by long-term exposure to various air pollutants.

Keywords: Cox proportional hazard model; Dietary diversity score; Mixture of air pollutants; Quantile g-computation approach; UK Biobank.