A large, population-based study in Catalonia, Spain has examined children and adolescents, between two and 17 years, who relocated between 2011–2018, the results suggesting a link between moving to areas with higher levels of air pollution and weight gain, particularly among the younger children.
The study was led by the Barcelona Institute for Global Health (ISGlobal) from where Martine Vrijheid, head of the Childhood and Environment research group, said: ‘A good way to investigate whether the two are linked is to see what happens when a child is suddenly exposed to higher or lower levels of air pollution as a result of moving to a different home address. This is what we call a natural experiment.’
From a starting point of slightly more than one million children, the number studied was whittled down to 46,644 once non-movers and multiple movers were excluded. Also not considered were those for whom there was insufficient BMI or air pollution data before and after (at least 180 days after) relocation.
The research team estimated the annual levels of NO2, PM10 and PM2.5 particulate matter in each participant’s home area, before and after moving. Weight and height is routinely measured at the primary care centers and this information was used to calculate BMI before and 180 days or more after the move.
The children were divided into three age groups: pre-school (2-5), school-age (6-11) and adolescent (12-17). The BMI of both the pre-school and school-age children was seen to increase after moving to a more polluted area, while no significant changes were seen for the older group.
In contrast, moving to less polluted areas had no significant effect on BMI.
Sarah Warkentin, ISGlobal researcher and first author of the study said: ‘This may be because reductions in air pollution levels seem to be less relevant for those who were already exposed to high levels of pollution.’
Strangely, it was noted that moving to areas with similar levels of air pollution was associated with decreases in BMI, particularly in the school-age group.
The researchers point out that the biological mechanisms that connect air pollution to weight gain are not fully understood, but they suggest that causes may may include ‘oxidative stress, inflammation of adipose tissue, reduced glucose uptake, hormonal disruption, changes in metabolism, or reduced lung function.’
Talita Duarte-Salles, head of the ‘Real World Epidemiology’ research group at Jordi Gol i Gurina Foundation said: ‘The data collected routinely by primary healthcare professionals allowed us to perform a very large natural experiment in a very large number of children and adolescents. This type of study could be replicated in the future to study the impact of the environment on other health problems.’