Lung function measurements in children - copsac
Lung function measurements in children - copsac
Lung function measurements in children - copsac
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<strong>function</strong> <strong>in</strong> childhood (6-10). One particular cohort study reported an asthma rate of 43%<br />
versus 8% and sensitization to common allergens of 45% versus 26% by age 13 years <strong>in</strong><br />
<strong>children</strong> with <strong>in</strong>fant hospitalization for RSV bronchiolitis compared with a matched control<br />
group (10). A review of pooled data from 10 controlled studies concluded that wheez<strong>in</strong>g (but<br />
not recurrent wheez<strong>in</strong>g) is more common after severe RSV bronchiolitis up till 5 years of<br />
follow-up (37). Two F<strong>in</strong>nish studies reported only marg<strong>in</strong>ally <strong>in</strong>crease <strong>in</strong> the prevalence of<br />
asthma after RSV bronchiolitis <strong>in</strong> <strong>in</strong>fancy (36, 38). On the other hand, predisposition to<br />
asthma and atopy was associated with <strong>in</strong>creased risk of lower respiratory tract <strong>in</strong>fection and<br />
hospitalization for RSV <strong>in</strong>fection (33, 39, 40) and early wheezy symptoms were found to be a<br />
strong risk factor for subsequent hospitalisation for RSV (32). Therefore the direction of<br />
causality is unknown: Does RSV <strong>in</strong>crease risk of asthma or is asthma constitution <strong>in</strong>creas<strong>in</strong>g<br />
the risk of severe response to RSV <strong>in</strong>fection, or are both shar<strong>in</strong>g a common undisclosed<br />
environmental exposure.<br />
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The model we used adjusted for genetic variation by analyz<strong>in</strong>g long-term outcome <strong>in</strong><br />
monozygotic tw<strong>in</strong> pairs, <strong>in</strong> which one <strong>in</strong>fant had been hospitalized for severe lung symptoms<br />
<strong>in</strong> response to verified RSV bronchiolitis, whereas the tw<strong>in</strong> sibl<strong>in</strong>g had not been hospitalized<br />
at any time for RSV bronchiolitis. This allowed a comparison of severe versus milder<br />
response to RSV <strong>in</strong>fection, genetic factors and environmental exposures dur<strong>in</strong>g follow-up<br />
years be<strong>in</strong>g equal between the co-habit<strong>in</strong>g MZ tw<strong>in</strong> proband and control pairs.<br />
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Our recent publication based on 8,280 tw<strong>in</strong> pairs showed that a model <strong>in</strong> which asthma<br />
“causes” RSV hospitalization fitted significantly better than a model <strong>in</strong> which RSV<br />
hospitalization “causes” asthma (41). On the other hand Wu and colleagues concluded <strong>in</strong><br />
another recent paper that they have shown strong evidence for causal relationship of w<strong>in</strong>ter<br />
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