Bad air pollution in China. (Photo : Getty Images)
Exposure to air pollution at one's home increases the risk of developing insulin resistance as a pre-diabetic state of type 2 diabetes, said a new study from Germany.
Scientists at the Helmholtz Zentrum München, in collaboration with colleagues of the German Center for Diabetes Research (DZD), reported these results in the journal Diabetes. They analyzed data from nearly 3,000 participants of the KORA study that live in the city of Augsburg and two adjacent rural counties.
"The results revealed that people who already have an impaired glucose metabolism, so-called pre-diabetic individuals, are particularly vulnerable to the effects of air pollution," said Dr. Kathrin Wolf, lead author of the study.
"In these individuals, the association between increases in their blood marker levels and increases in air pollutant concentrations is particularly significant! Thus, over the long term -- especially for people with impaired glucose metabolism -- air pollution is a risk factor for type 2 diabetes."
All individuals were interviewed and physically examined. Researchers also took fasting blood samples in which they determined various markers for insulin resistance and inflammation.
In addition, leptin was examined as adipokine, which has been suggested has an association with insulin resistance. Non-diabetic individuals underwent an oral glucose tolerance test to detect if their glucose metabolism was impaired.
Researchers then compared their data with concentrations of air pollutants at the place of residence of the participants. They estimated the air pollutant concentration using predictive models based on repeated measurements at 20 sites (for particle measurements) and at 40 sites (for nitrogen dioxide measurements) in the city and in the rural counties.
"Whether the disease becomes manifest and when this occurs is not only due to lifestyle or genetic factors, but also due to traffic-related air pollution," said Prof. Annette Peters, director of the Institute of Epidemiology II at Helmholtz Zentrum München and head of the research area of epidemiology of the DZD.
The authors are concerned that concentrations of air pollutants, though below EU threshold values, are still above the proposed guidelines of the World Health Organization (WHO). As a consequence, they demand changes in government policy.
"Lowering the threshold for acceptable air pollution levels would be a prudent step," said Dr. Alexandra Schneider, who was also involved in the study.
"We are all exposed to air pollution. An individual reduction by moving away from highly polluted areas is rarely an option."
Scientists next want to investigate the influence of ultrafine particles.
"Diabetes will be a main focus of our research, also in this context. A precise knowledge of the risk factors is crucial for counteracting the increasing incidence of diabetes," said Peters.
A previous study of Helmholtz Zentrum München from 2013 showed that ultrafine particulate air pollution increases the risk of insulin resistance in childhood. In a meta-analysis from 2015 the same authors concluded that there is an association between long-term exposure to air pollutants and the development of type 2 diabetes.
