wheezing episodes) in infants, are virtually unknown. To determine the trend of RW prevalence and
severity of RW in infants during the first year of life between two surveys separated by seven years.
Method: This is a part of International Study of Wheezing in Infants (EISL), a population-based
study, in infants aged 12-15 months, compares data from two surveys (S1 and S2) performed using
the same methodology, in three large cities that participated in both surveys: Curitiba and São Paulo
(Brazil) and Santiago (Chile).
Results: The average prevalence of wheezing once or more during the first year of life decreased
from 52.9% (95%CI 51.8-54) in S1 to 46.9% (95%CI 45.2-48.07) in S2, p = 0.0001. There was a
significant decrease in the mean prevalence of RW between S1 (23.3%, 95%CI 22.3-24.3) and S2
(20.4%, 95%CI 19.0-21.8), p=0.004. In infants with RW the mean prevalence of severity markers
between S1 and S2 remained high (severe episode: 56.9% to 54.2%, p = 0.32); ED visits (68.1% to
70.9 %, p = 0.21), with a significant increase in admissions for wheezing (21.1% to 26.7%, p =
Conclusion: the prevalence of RW and severity markers during the first year of life remained high
between both surveys. The infants who suffer from RW have markedly high prevalence of severity
markers as visits to ED and admissions for wheezing, indicating that an important group of these
infants has a troublesome progression that certainly affect quality of life and put infants at risk of
more severe complications.