Young children with respiratory tract infections such as colds and pneumonia may be at an increased risk of developing asthma and weak lung function in later life, says a study.

The study of 154,492 European children found that those who had upper respiratory infections, such as colds, sinusitis, laryngitis, tonsillitis, pharyngitis and otitis, by the age of five years had a 1.5-fold increased risk of developing asthma in later life.

Children who had suffered from lower respiratory tract infections, such as bronchitis, bronchiolitis, pneumonia and general chest infections, had a two- to four-fold increased risk of developing asthma in later life and were also more likely to have worse lung function, according to the findings presented at the European Respiratory Society International Congress in Milan, Italy.

“These findings support the hypothesis that early-life respiratory tract infections may influence the development of respiratory illnesses in the longer term,” said Evelien van Meel from Erasmus MC University Medical Centre, The Netherlands.

“In particular, lower respiratory tract infections in early life seem to have the greatest adverse effect on lung function and the risk of asthma,” van Meel said.

The researchers analysed data from 37 groups of children from several European countries who were born between 1989 and 2013.

Children were included in this analysis if data were available on respiratory tract infections in early life (from age six months up to five years old), and childhood lung function and/or asthma.

The length of follow-up varied between groups, but ranged from birth until the age of four to 15 years.

Lung function and asthma are two different measures of respiratory health and are only partly related.

“Lung function is an objective measure of the function of the lungs and airways. Lung function could be affected without leading to symptoms, or it could lead to asthma or other complaints such as wheezing,” van Meel said.

“Additionally, a child could be diagnosed with asthma but their lung function could be fairly unaffected, for example because they are taking adequate asthma medications,” van Meel added.