It is now widely accepted that bronchiolitis is associated with future progression to recurrent wheezing and asthma [
4‐
6]. Over the years, several studies have explored the risk factors associated with recurrent wheezing or asthma in children with bronchiolitis in their early life [
7‐
19]. Some of these studies have suggested that the severity of bronchiolitis is related to recurrent wheezing in future [
13,
14,
20,
21]. Be’er [
17] reported that children admitted to the pediatric intensive care unit for bronchiolitis were more likely to be associated with asthma in early life.
In this study, we found that older maternal age (> 26.5 years old) may be associated with recurrent wheezing in children diagnosed with bronchiolitis in early life but was not an independent risk factor. Another study [
22] examined the association between maternal age and asthma and concluded that maternal age less than 20 years old was a protective factor. The reason for this is still unclear and further research is needed.
It is known that atopic status is associated with recurrent wheezing. A previous review [
23] indicated that atopic status and genetics play a decisive role in recurrent wheezing and asthma. Singla [
24] examined 260 children with recurrent wheezing and reported 35% with allergic rhinitis. Chen [
15] found that the history of eczema was the only independent risk factor among the factors they selected. Moreover we found that allergic history, atopic dermatitis, allergic rhinitis and atopic family history were all related to recurrent wheezing after bronchiolitis and the latter three were independent risk factors. Therefore this suggests that for infants with allergic history, atopic dermatitis, allergic rhinitis or atopic family history, more active measures should be taken to prevent the occurrence of recurrent wheezing after bronchiolitis. However, according to our research, skin prick test, FeNO and blood eosinophil counts were not significantly associated with recurrent wheezing after bronchiolitis. Pesonen [
25] found skin prick test positivity in children aged 5 years could predict recurrent wheezing at the age of 11 and 20 years. In contrast, our study involved a skin prick test for infants/toddlers, and maybe the accuracy of the test needed to be evaluated by following up the results of this test when the children grow up. A cohort study [
26] concluded that sedated single-breath FeNO in infants/toddlers could predict asthma at the age of 6 years. However, in another review [
27], they identified that FeNO was used only to estimate eosinophil inflammation rather than asthma. Gaillard [
28] suggested that blood eosinophil counts in infants with wheezing were a risk factor for persistent wheezing at school age. Wagener [
29] found that blood eosinophil counts were highly correlated with those in sputum considered a widely used biomarker for asthma [
27]. Midulla [
30] reported that blood eosinophil counts were the main risk factors for recurrent wheezing in children diagnosed with bronchiolitis; however it has also been suggested that the alveolar lavage fluid eosinophil counts may have a limited value in predicting recurrent wheezing [
31]. Piippo-Savolainen [
32] found that blood eosinophil counts during bronchiolitis were not related to recurrent wheezing in adults. In conclusion, more researches should be conducted on the effects of skin prick test, FeNO and blood eosinophil testing during bronchiolitis on recurrent wheezing in the future.
In our analyses, a parallel analysis of the two groups showed that the predominant bacterial species in the nasopharynx were Streptococcus pneumoniae, Staphylococcus aureus, Moraxella catarrhalis and Haemophilus influenzae. Infection or colonization of Moraxella catarrhalis was a risk factor for later recurrent wheezing in children with bronchiolitis. Previous studies on airway microbiota have implicated Moraxella catarrhalis as a risk factor for wheezing and asthma using both cross-sectional and prospective study designs [
33‐
35]. Moraxella catarrhalis was found to be associated with chronic wheezing in children’s later life [
33,
34] which was also confirmed in our study.