China: Study on Air Pollution and Type 2 Diabetes

A recent study in BMC Medicine has suggested that reducing exposure to air pollution before type 2 diabetes and diabetes complications may lead to good lifetime longevity by reducing premature mortality risk.

The study found that exposure to ambient air pollution results in an increased risk of incidence and progression of type 2 diabetes (T2D), but to various extents for different progressions.

There has been proper documentation of the association between air pollution and incident T2D. Still, the evidence of the association with the development of ensuing diabetes complications and post-diabetes mortality is inadequate. A research team led by Yinglin Wu, Sun Yat-sen University, Guangzhou, China, therefore aimed to examine the association between air pollution and different progressions and outcomes of type 2 diabetes.

The analysis included 398,993 participants free of diabetes and diabetes-related events at recruitment based on the UK Biobank. Utilizing data from the Department for Environment, Food and Rural Affairs in the UK, the researchers estimated exposures to particulate matter with a diameter ≤ 10 μm (PM10), PM2.5, nitrogen oxides (NOx), and NO2 for each transition stage at each participant's residential addresses.

Outcomes included diabetes complications (diabetic eye disease, diabetic kidney disease, peripheral vascular disease, diabetic neuropathy disease, metabolic events, and cardiovascular events), incident T2D, cause-specific mortality, and all-cause mortality. The impact of air pollution was analyzed on different T2D progressions. Also, the cumulative transition probabilities of different T2D stages were estimated under different air pollution levels.

Study Findings

• 13,393 incident T2D patients were identified during the 12-year follow-up, of whom 3,791 developed diabetes complications and 1,335 died.
• Air pollution was shown to be associated with different progression T2D stages with different magnitudes.
• In a multivariate model, the hazard ratios per interquartile range elevation in PM2.5 were 1.63 and 1.08 for transitions from healthy to T2D and from T2D to complications, and 1.50, 1.49, and 1.54 for mortality risk from baseline, T2D, and diabetes complications, respectively.
• Stronger estimates of four air pollutants were observed on the transition from the baseline to incident T2D than on other transitions.
• The researchers found significant associations between four air pollutants and mortality risk due to cardiovascular diseases and cancer from T2D or diabetes complications.
• People with higher levels of air pollution exposure generally had higher cumulative transition probability.

The study provided some novel discoveries by showing positive associations between air pollutants (PM2.5, PM10, NOx, and NO2) and different stages of transition from healthy to type 2 diabetes, to diabetes complications, and then to death.

The researchers quantified the cumulative probabilities of five transitions. They discovered that participants with higher levels of air pollution exposure might be at increased adverse diabetic outcomes risk, specifically the risk of diabetes mortality and complications.

Reference

Wu, Y., Zhang, S., Qian, S.E. et al. Ambient air pollution associated with incidence and dynamic progression of type 2 diabetes: a trajectory analysis of a population-based cohort. BMC Med 20, 375 (2022). https://doi.org/10.1186/s12916-022-02573-0