Urban environments increase risk of developing asthma, says study

The combination of air pollution, dense urban development and limited green spaces increases the risk of asthma in both children and adults, according to a new study.

Improving these can help prevent one in 10 cases of asthma -- a chronic respiratory condition characterised by inflammation and narrowing of the airways, making breathing difficult.

Previous studies have typically calculated the risk of one environmental factor at a time. The new study combined several environmental factors and described how they together affect the risk of developing asthma.

This provided a better picture of environmental risks, as life in a city usually involves exposure to several environmental risk factors at the same time

Researchers from Karolinska Institutet, in Sweden, found that 11.6 per cent of asthma cases could be explained by the combination of environmental factors.

In other words, in a favourable environment, approximately one in ten people with asthma would not have developed the disease.

The combination of air pollution, lack of green spaces, and dense urban development was most relevant for the development of asthma.

“This finding is useful for politicians and others involved in urban planning. The method makes it possible to identify risk areas in existing urban areas, but it can also be used when planning future urban environments,” said Erik Melén, professor at the Department of Clinical Research and Education.

The study covered nearly 350,000 people of different ages, from 14 cohorts in seven European countries.

Information on home addresses of each individual made it possible to link data on various environmental risks in the urban environment to individual people.

The environmental exposures included were air pollution, outdoor temperatures, and the level of urban density. The assessment was partly based on satellite images showing grey, green, or blue areas, i.e., where there were buildings, green spaces, or water.

During the study period, nearly 7,500 of the study participants developed asthma as children or adults. The researchers found

The researchers next aim to examine blood samples from some of the study participants to identify their metabolome, that is, a composite picture of the body's metabolism and breakdown products.

The purpose is to understand how external environmental factors affect the body, which could provide a better understanding of how asthma develops.