Due to little information on the combined effects of air pollution and habitual physical activity on type 2 diabetes development, the risk-benefit relationship has become an important public health concern as over 91% of the world’s population live in places where WHO guidelines on air quality are not met.
The study aimed to examine the combined associations of regular physical activity and chronic exposure to ambient particulate matter with a diameter less than 2.5 μm (PM2.5 particles) with the incidence of type 2 diabetes.
The participants were 156,314 adults in Taiwan, where the annual PM2.5 concentration is around 2.6 times higher than the WHO recommended limit. They had undergone a total of 422,831 medical examinations.
Diabetes diagnoses were identified from medical examinations, while two-year mean PM2.5 exposure was estimated at each participant’s address using a satellite-based model. Information on physical activity and a wide range of other variables was collected using a standard self-administered questionnaire.
Findings showed that moderate and inactive/low physical activity were associated with a 31% and 56% higher risk of diabetes, respectively. Participants exposed to moderate and high PM2.5 had a 31% and 94% higher risk of type 2 diabetes than those exposed to low PM2.5.
Whereas those with high physical activity and low PM2.5 had a 64% lower risk of type 2 diabetes.
The authors highlight that the benefits of habitual physical activity on type 2 diabetes remained stable in participants with different levels of PM2.5 exposure.
Further analysis revealed that the effect on diabetes risk increased for higher pollution levels than for lower levels of physical activity.
Pollution can cause system-wide inflammation throughout the body, including the lungs, blood vessels, and central nervous system. However, the researchers believe that the metabolic improvements caused by physical activity prevent the development of diabetes because pollutants inhaled during exercise are only a small fraction of those inhaled overall by a person.
They conclude, “Our findings suggest that habitual physical activity is a safe strategy for diabetes prevention for people who reside in relatively polluted areas and should be promoted. Our study reinforces the importance of air pollution mitigation for diabetes prevention.”
The authors emphasize the urgent need for health guidelines, especially in regions with significant air pollution, to inform people if regular physical activity is beneficial.