CommentaryRespiratory syncytial virus in early life and risk of wheeze and allergy by age 13 years
Introduction
During the first 3 years of life, most lower respiratory tract illnesses with wheezing are associated with infection with the respiratory syncytial virus (RSV).1, 2, 3, 4 Although many studies have reported an association between lower respiratory tract illnesses in early life and subsequent recurrent episodes of wheezing,5, 6, 7 most of these studies were based either on retrospective surveys6 or on groups of children admitted to hospital with severe lower respiratory tract illnesses.5, 7 The nature of the association between RSV lower respiratory tract illnesses in early life and the subsequent development of recurrent wheezing episodes and asthma is not known. The risk of subsequent wheezing after RSV lower respiratory tract illnesses may decrease significantly with increased age,8 but no studies have directly addressed this issue. Similarly, some studies have suggested that RSV lower respiratory tract illnesses are associated with increased risk of subsequent allergic sensitisation,9, 10 but this association is unconfirmed.5, 6
Children with RSV lower respiratory tract illnesses in early life have a lower level of lung function later in life.6, 11, 12 Lung-function tests in infants before any lower respiratory tract illness suggest that some children who subsequently develop such illness start life with a lower level of lung function.13, 14, 15 Whether deficits in lung function associated with wheezing lower respiratory tract illnesses in early life are due to alterations in airway tone, and thus reversible after use of bronchodilators, or whether they are otherwise fixed and unrelated to airway tone, is not known.
We assessed recurrent wheezing, atopy status, and lung function in children who had had confirmed viral lower respiratory illnesses during the first 3 years of life. Our main hypothesis was that RSV lower respiratory tract illnesses are associated with a diminishing risk of recurrent wheezing during school years. Our secondary hypothesis was that RSV lower respiratory tract illnesses are unrelated to the risk of subsequent development of atopic sensitisation, but are associated with a lower level of lung function at a mean age of 11 years.
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Study participants
The children included in our study were a subset of the 1246 children born in 1980–84 and enrolled in the Tucson Children's Respiratory Study.16 The enrolment process and study design are described elsewhere.2, 16 Birthweight, maternal educational attainment, and family history of asthma were obtained from parents by questionnnaire after each child was born.
Children were assessed by their paediatrician whenever they had signs or symptoms of lower respiratory tract illnesses (deep or wet chest
Results
888 of the original 1246 children enrolled were followed for the first 3 years of life. 519 (58·5%) had at least one lower respiratory tract illness, but only 472 (90·9%) had recorded tests for viruses and other agents. Of these 472 children, 207 (43·9%) had RSV lower respiratory tract illness, 68 (14·4%) had para-influenza lower respiratory tract illness, 68 (14·4%) had lower respiratory tract illness caused by other agents (adenovirus, influenza, chlamydia, cytomegalovirus, rhinovirus,
Discussion
We showed that RSV lower respiratory tract illnesses before age 3 years are associated with a significant increase in risk of subsequent wheezing during the first 10 years of life. The association was equally strong for both infrequent and frequent wheezing, but rapidly subsided with age and was not significant by age 13. Similar trends were observed for lower respiratory tract illnesses due to other viruses or during which no agents were isolated, but these were less marked and less consistent
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