Early-life respiratory infections have been linked with later development of respiratory diseases in a meta-analysis of more than 150,000 children, but some questions still need to be answered before any changes in clinical practice are warranted, researchers say.
A team of international researchers explored associations of upper and lower respiratory tract infections in children aged 6 months to 5 years with FEV1, FVC, FEV1/FVC, FEF75 and asthma later in life when they were of school age (4 to 15 years; median age 7).
They found that children with early-life lower respiratory tract infections had a lower school-age FEV1, FEV1/FVC and FEF75, and that there was a higher increased risk of school-age asthma compared with those who had had upper respiratory tract infections.
Dr Bushra Ahmed, an Academic Clinical Lecturer in Paediatric Respiratory Medicine at University College London, told the limbic that findings of the “well-designed” study “add significantly to a growing body of evidence that early life respiratory infections of any severity, particularly of the lower respiratory tract, are associated with asthma and lower lung function in later childhood”.
For the study, published in European Respiratory Journal, the researchers obtained information on early-life respiratory tract infections at 6 months, 1, 2, 3, 4 and 5 years, mostly via questionnaires but also from registry data or interviews.
School age lung function and asthma were then assessed with information on spirometry and FEV1/FVC, FEV1/FVC and FEF75, largely obtained via questionnaires but also registry data, interviews and symptom diary or report. Measurements were adjusted for sex, age, height and ethnicity.
The findings showed that lower respiratory tract infections at all ages were linked with a lower FEV1 and FEV1/FVC (range in Z-score difference -0.09 to -0.30), but only lower respiratory tract infections at age 1 year were associated with a lower FVC (-0.08). Lower respiratory tract infections at all ages, with the exception of at 6 months, were also linked with a lower FEF75 (range: -0.12 to -0.24).
While both upper and lower respiratory tract infections in early life were associated with the development of asthma, the risk was significantly greater with infections in the lower tract, with OR ranges of 2.10 – 6.30 versus 1.25 to 1.57, respectively, the research showed.
The authors concluded that early-life upper respiratory tract infections are associated with an increased risk of school-age asthma, while early-life lower respiratory tract infections are linked with lower lung function at school-age, “indicative of airway obstruction and airflow limitation”, and an even stronger risk of asthma.
Furthermore, the results “were not modified by wheezing in early-life suggesting that these associations could in part be present irrespective of possible early-life susceptibility to asthma”, the researchers noted.
All-in-all, the findings “suggest that predominantly lower respiratory tract infections could have a direct effect on lung development, and subsequent chronic respiratory diseases”, they wrote.
However, Dr Ahmed told the limbic that important questions still need to be addressed before any changes in clinical practice are warranted.
“One of the challenges is in demonstrating whether such infections cause an increased risk of asthma and lower lung function, or vice versa, and the mechanisms which underpin this. Although the authors attempted to account for preceding infections in their analyses, this could not be answered fully with this study,” she said.
Also, “Van Meel and colleagues do not report any microbiology data, [which] would be useful as the association between infections, asthma and lung function may relate to the specific organisms as has been found in previous studies.
“These questions are important to address before advocating for changes to the clinical management of infants with respiratory tract infections to better understand which therapeutic interventions would be effective to prevent the development of chronic lung disease,” she stressed.