Growing areas where air pollution is prominent increase the risk of insulin resistance (the predecessor to diabetes) in children.

The finding was published in the journal Diabetologia, of the European Association for the Study of Diabetes (EASD), and was led by a group of researchers from Germany.

Earlier research has shown associations between air pollution and other chronic issues like heart disease and atherosclerosis. Currently, epidemiological studies that have analyzed links between long-term exposure to traffic-related air pollution and type 2 diabetes in adults have had conflicting results. Studies on insulin resistance in kids are generally rare.

A study published just last month suggested that in the U.S., many citizens are living in unhealthy cities. Overall most Americans are now breathing cleaner air, however, some are living in cities that are more polluted than they were a decade ago.

Additionally fetal exposure to air pollution has also been linked to many pediatric cancers, such as acute lymphoblastic leukemia, as well as low birthweight in babies.

The current study looked to examine the potential link between air pollution and insulin resistance in children.

Researcher Joachim Heinrich said:

"Although toxicity differs between air pollutants, they are all considered potent oxidisers that act either directly on lipids and proteins or indirectly through the activation of intracellular oxidant pathways. Oxidative stress caused by exposure to air pollutants may therefore play a role in the development of insulin resistance. In addition, some studies have reported that short-term and long-term increases in particulate matter and nitrogen dioxide (NO2) exposure lead to elevated inflammatory biomarkers, another potential mechanism for insulin resistance."

The investigators collected fasting blood samples from 397 children all aged 10 years and from within a follow-up of two German birth cohort studies. They estimated personal-level exposures to traffic-related air pollution at their home addresses.

They did this by examining emissions from road traffic in the neighborhood as well as population density and land use in the area. The link between air pollution and insulin resistance was configured using a model adjusted for many potential confounders such as:
  • birthweight
  • socioeconomic status of the family
  • BMI
  • pubertal status
  • second-hand smoke exposure in the home
The researchers found that in all adjusted and raw models, levels of insulin resistance were higher in children with greater exposure to air pollution. Insulin resistance was higher by 17% for every 10.6 µg/m3 (2 standard deviations [SDs] from the mean) rise in ambient nitrogen dioxide (NO2) and 19% for every 6 µg/m3 (2 SDs) rise in particulate matter of up to 10 μm in diameter.

Proximity to major roads raised insulin resistance by 7% per 500 meters. All these findings were statistically significant, according to the authors.

Heinrich concludes:

"There is some evidence that air pollution is associated with lower birthweight and growth restrictions - also shown previously in one of the cohorts of the present study - which are known risk factors for type 2 diabetes. Thus, one may speculate that lower birthweight is an intermediate step or 'phenotype' between air pollution and insulin resistance. However, we found no evidence to suggest that this may be true in our cohort of children, all of whom had birthweights above 2.5kg.

To our knowledge, this is the first prospective study that investigated the relationship of long-term traffic-related air pollution and insulin resistance in children. Insulin resistance levels tended to increase with increasing air pollution exposure, and this observation remained robust after adjustment for several confounding factors, including socioeconomic status, BMI and passive smoking."

15 year follow-ups of both cohorts are currently on-going. The authors plan on examining how their results translate into older age during or after puberty. Henrich says, "Moving from a polluted neighborhood to a clean area and vice versa would allow us to explore the persistence of the effect related to perinatal exposure and to evaluate the impact of exposure to increased air pollution concentration later in life."

Written by Kelly Fitzgerald