medwireNews: Research shows that childhood lower respiratory tract infections (RTIs) are associated with impaired lung function in adulthood, but only when they occur in the first year of life.
The prospective UK study included 581 participants who had been followed up to the age of 5 years, including 14 occasions when data on infections were collected. At the age of 25 years, the researchers measured forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1 to FVC ratio, forced expiratory flow 25% to 75% (FEF25%–75%), and peak expiratory flow (PEF).
A history of lower RTI in the first 5 years of life was significantly and negatively associated with all measures of lung function, except for FVC, report Yoav Ben-Shlomo (University of Bristol, UK) and colleagues.
When the authors stratified the results by age at infection, there was a significant relationship between lower RTIs in the first year of life and all measures of lung function. But, other than an association between PEF and lower RTI at the age of 2 to 5 years, there were no associations with lung function in any of the other age groups.
And a test for interaction effects confirmed that there may be a “sensitive period” of exposure to lower RTIs regarding their subsequent effects on FEV1, FEF25%–75%, and PEF.
There was also some evidence for an effect of upper RTIs on FEV1/FVC, particularly in the first year of life, during which there was also a relationship between these infections and FEF25%–75%.
The authors say that their findings support the theory that infections in early childhood lead to lung damage, such as acute lung inflammation and remodeling, resulting in lower adult lung function.
“Our findings of strong associations and apparent dose–response effects in the fully adjusted analysis would support this causal explanation,” they write in the Annals of Epidemiology.
In particular, the age-dependent effect could indicate that the early lung damage interferes with alveolar multiplication, a process that is thought to complete around the age of 2 years. They also note that the finding may be a case of reverse causation in which children with pre-existing reduced lung function are more susceptible to lower RTIs.
If further research reveals there is a causal effect, it could have important public health implications, the authors say.
“Public health interventions to limit LRTIs, such as reducing overcrowding, parental education, and increasing immunization of children, particularly if targeted at infants in the first year of life, may reduce morbidity and mortality attributable to [chronic obstructive pulmonary disease],” they conclude.
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