Risk Factors for Recurrent Wheezing in Infants

Abstract

Introduction: wheezing is one of the most common respiratory symptoms in childhood. Regardless of the cause, it is a reason to seek medical care in emergency rooms, especially if there is recurrence of episodes. Very common in childhood, recurrent wheezing has its first episodes in the first year of life. We sought to examine the risk factors for recurrent wheezing in infants in the first year of life. Methods: this is a cross-sectional quantitative study in which a standardized questionnaire of the International Study of Wheezing in Infants, translated and validated in Brazil, consisting of objective questions, applied 40 mothers were enrolled in two Family Health units. Results: the risk factors found were: smoking during pregnancy, family history of asthma, rhinitis and allergic dermatitis, the presence of at least one pet in the home at the time of birth and age at first cold less than or equal to three months of life. No significant relationships were found between males and wheezing, exclusive breastfeeding or numbers of colds in the first year of life. Conclusion: our findings are different from those reported in the literature.

Full text

Risk factors for recurrent wheezing in infants Journal of Human Growth and Development 2013; 23(2): 203-208
– 203 -
RISK FACTORS FOR RECURRENT WHEEZING IN INFANTS
Wellyne Alves Lustosa1, Marta Lígia Vieira Melo1, Ubiraídys de Andrade Isidório2,
Milena Nunes Alves de Sousa3, Luiz Carlos de Abreu4, Vitor E. Valenti4,5,
Marco A. Cardoso5, Elisangela Vilar de Assis4
1 Faculdade Santa Maria, Cajazeiras, PB, Brasil.
2 Universidade Cruzeiro do Sul, São Paulo, SP, Brasil.
3 Universidade de Franca, Franca, SP, Brasil.
4 Faculdade de Medicina do ABC, Santo André, SP, Brasil.
5 Programa de Pós-Graduação em Fisioterapia, Faculdade de Ciências e Tecnologia, UNESP, Presidente Prudente, SP, Brasil.
Corresponding author: ely.vilar@hotmail.com
Suggested citation: Lustosa WA, et al. Risk factors for recurrent wheezing in infants; Journal of Human Growth and Development
2013; 23(2): 203-208
Manuscript submitted Dec 16 2012, accepted for publication May 10 2012.
Journal of Human Growth and Development
2013; 23(2): 203-208 ORIGINAL RESEARCH
Abstract
Introduction: wheezing is one of the most common respiratory symptoms in childhood. Regardless
of the cause, it is a reason to seek medical care in emergency rooms, especially if there is recurrence
of episodes. Very common in childhood, recurrent wheezing has its first episodes in the first year of
life. We sought to examine the risk factors for recurrent wheezing in infants in the first year of life.
Methods: this is a cross-sectional quantitative study in which a standardized questionnaire of the
International Study of Wheezing in Infants, translated and validated in Brazil, consisting of objective
questions, applied 40 mothers were enrolled in two Family Health units. Results: the risk factors
found were: smoking during pregnancy, family history of asthma, rhinitis and allergic dermatitis, the
presence of at least one pet in the home at the time of birth and age at first cold less than or equal
to three months of life. No significant relationships were found between males and wheezing, exclusive
breastfeeding or numbers of colds in the first year of life. Conclusion: our findings are different
from those reported in the literature.
Key words: risk factors; wheezing; infants; respiratory sounds.
INTRODUCTION
Wheezing is one of the most common respi-
ratory symptoms in childhood and may result or
not from any one of various lung diseases. Rcurrent
wheezing is a very common condition in childhood
and, in most cases, their first episodes occur in the
first year of life1.
The studies of Medeiros et al2 have demon-
strated several risk factors for early wheezing in
children and its relationship to the subsequent de-
velopment of asthma, such as prematurity, mater-
nal smoking during pregnancy or after birth liabili-
ties, males, respiratory infections. Relationship has
also been demonstrated between wheezing and
early sensitization to food and aeroallergens, re-
duced lung function and higher blood level of eosi-
nophils, with subsequent persistence of these symp-
toms3,4.
There are few population-based studies in
which the prevalence of wheezing in infants has been
assessed, and are even fewer with similar method-
ologies to compare populations from several differ-
ent localities. The first organized multicenter and
multinational study with this objective was the
Estudio Internacional de Sibilancias en Lactantes
(EISL, International Study of wheezing in infants).
With the use of validated questionnaires for com-
munities, the author’s sought to determine the
prevalence of recurrent wheezing, clinical features,
risk factors and the association of wheezing with
respiratory infections in infants in Latin America and
some countries in Europe during the first 12 months
of life5,6.
Chong Neto et al.7 found that the preva-
lence of wheezing in infants was 45.4%, with on-
set of seizures at 5.5 months. The number of
wheezing children who had three or more seizures
was 22.6%, higher than in developed countries,
but lower than that found in Chile among low-
income families8,9. Bianca et al.10 after using the
standardized protocol of EISL observed one or

Risk factors for recurrent wheezing in infants Journal of Human Growth and Development 2013; 23(2): 203-208
– 204 -
more episodes of wheezing in the first 12 months
of life in 467 infants (46.0%) with mean age of
symptom onset of 5.0 ± 3.0 months.
The following gestion emerged in the light
above, mentioned studies: what are the possible
risk factors that trigger wheezing in infants in the
first year of life?
The undertaking of this research is justified
by the high incidence and prevalence of wheezing
in infants worldwide, leading to consequences for
mother and child, as well as because bath wheez-
ing in asthma is indicative of a more advanced stage
of a child’s life, can make it a public health prob-
lem, which calls for an investigate ton of its risk
factors in infants up to 12 months. Therefore, we
sought to determine the risk factors for wheezing
in infants in their first year of life.
METHODS
The study was conducted in three Family
Health Units (USFs) in Cajazeiras, PB, Brazil. Health
units were selected for as they observe a larger
number of people per unit area. The visits to the
units took place in the days of checking the weight
of the children in the period determined by each
USF.
Among all the parents/guardians only 40
agreed to participate. We included infants of both
genders, aged 12 to 24 months of and excluded
infants born from mothers younger than 18 years
old and older than 40 and infants with neurological
and/or cardiovascular disorders.
We used a standardized questionnaire of the
EISL, consisting of objective questions translated
from Spanish into Portuguese and validated in Bra-
zil by Chong Neto et al.6.
The instrument consists of 39 questions on
wheezing and respiratory symptoms, lifestyle hab-
its of the mother during pregnancy, use of medica-
tions, medical diagnoses and risk factors to be an-
swered by the parents and/or guardians of the
infants. The question is related to the period in which
the children were under 12 months old.
Data were presented by using descriptive and
inferential statistics. We used the Statistical Pack-
age for Social Sciences (SPSS) for Windows, ver-
sion 15.0. For descriptive procedures we presented
gross and relative measures (frequencies and per-
centages), measures of central tendency (mean)
and variability (standard deviation and confidence
intervals minimum and maximum). The procedures
of statistical inference, were performed by means
of tests: Chi-Square calculation of prevalence ra-
tios and Mann-Whitney. The chi-square that esti-
mates association between variables, whereas the
prevalence ratio compares groups that had been
exposed to particular event (in this case, wheez-
ing) with those who had not presented such expo-
sure or that characteristic. The Mann-Whitney test
compares two groups metric variables, the choice
being determined by the effective guided test
sample. For the interpretation of the information,
we adopted a confidence interval of 95% and a sig-
nificance level of 5% (p <0.05).
RESULTS
We interviewed 40 parents of children of 12-
24 months old, although, the information obtained
were related to the first year of life. The majority of
children were male (52.5%) and Caucasians
(69.2%). The 40 children who participated in the
survey were divided almost equally into two groups:
wheezing (57.5%) and non-wheezing (42.5%).
With the purpose of to estimating the char-
acteristics and symptoms related to wheezing, we
calculated the prevalence ratio for the two groups:
(1) those who reported wheezing in the past 12
months, named wheezing, and (2) those who
showed no such symptom, non-wheezing. Initially,
we verified the association of these groups with the
gender and race of the participants. The estimated
prevalence ratio was not significant, so we cold not
assume that certain gender or race had a higher
chance of presenting wheezing. The descriptive and
inferential data are detailed in Table 1.
Table 1: Evaluation of the prevalence of wheezing due the gender and race
Variables Esp. Wheezing Non-wheezing RP IC95% p
f % f % Mín. Máx.
Gender Male 13 32.5 8 20.0
1.17 0.68 2.02 0.55
Female 10 25.0 9 22.5
Ethnicity White 15 38.5 12 30.8 0.95 0.53 1.71 0.87
1.17 0.68 2.02 0.55
With respect to group (1), the majority had
less than three episodes of wheezing bronchitis had
(39.1%), while 30.4%, each, presented 3-6, or
more than six episodes. It was found that the aver-
age age to present with such symptoms was 3.83
months (SD = 3.01), having children who presented

Risk factors for recurrent wheezing in infants Journal of Human Growth and Development 2013; 23(2): 203-208
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them at 1 month (minimum) or 11 months (maxi-
mum). We asked them, parther, to calculate, how
many times they had agreed the night due to cough-
ing or wheezing baby, they reported: 21.7% re-
ported that they never slept, 30.4% reported be-
ing woken up several times, 34.8% sometimes,
while 13.0% reported that they often agreed with
such a problem.
It was found that the majority of children
(73.9%) were brought to an emergency service
because of severe chest wheezing. 65.2% of
claimants reported observing dyspnea (shortness
of breath) in children, while 26.1% of children
have been hospitalized for bronchitis. However, it
was found that only 26.1% of them were diag-
nosed as having asthma. Such information is given
in Table 2.
Table 2: Aspects related to wheezing in children up to 12 months
Variables Yes No
F% f %
Search emergency service 17 73.9 6 26.1
Dyspnea 15 65.2 8 34.8
Hospitalized for bronchitis 6 26.1 17 73.9
Diagnosed with asthma 6 26.1 17 73.9
Wheezing was assessed in terms of expo-
sure to smoke in the environments of children,
prior to his/her birth or not. It was found that
having a smoker or resident parent as a smoker
does not constitute a factor that increases the
prevalence of wheezing, however, it was found
that the mothers’ having smoked during preg-
nancy doubles the chances of the baby’s present-
ing wheezing.
A family history of asthma, rhinitis and aller-
gic dermatitis was also considered to be associated
the prevalence of wheezing. All these variables con-
stituted as significant factors for the development
of wheezing, suggesting twice as likely. It was found
that relatives who had asthma, rhinitis or allergic
dermatitis presented nearly twice the prevalence
of wheezing, compared to those who did not. The
inferential data are shown in Table 3.
We evaluated in groups with no wheezing,
characteristics related to childbirth, immunization
and contact with animals. Regarding vaccination and
contact with animals, no significant associations
between these variables and wheezing, so we can
not affirm that provide updated vaccination or have
Table 3: Prevalence of wheezing in environments with exposure to smoke / fumes and depending on
family history
Variables Group Wheezing Not Wheezing RP IC95% p
f % f % Mín. Máx.
Resident Smoker Yes 11 27.5 6 15.0 1.24 0.73 2.09 0.52
No 12 30.0 11 27.5
Mother’s smoker Yes 6 15.0 5 12.5 0.93 0.50 1.73 0.81
No 17 42.5 12 30.0
Smoking in pregnancy Yes 5 12.5 0 0.0 1.94 1.40 2.68 0.04*
No 18 45.0 17 42.5
Familiar with Asthma Yes 13 32.5 3 7.5 1.95 1.14 3.30 0.01*
No 10 25.0 14 35.0
Familiar with rinithes Yes 15 37.5 5 12.5 1.87 1.03 3.39 0.02*
No 8 20.0 12 30.0
Familiar with dermatitis Yes 5 12.5 0 0.0 1.94 1.40 2.68 0.04*
No 18 45.0 17 42.5
contact with animals constitute risk factors or pro-
tective to present wheezing.
Nevertheless, there was an association of
wheezing in relation to mode of delivery and have
had contact with animals at birth. First, as child-
birth, it was found that cesarean delivery is config-
ured as a protective factor for wheezing. That is,
someone not born by cesarean section, is more
likely to have wheezing.

Risk factors for recurrent wheezing in infants Journal of Human Growth and Development 2013; 23(2): 203-208
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In relation to contact with animals at the
time of birth, the effect is opposite: a risk factor.
The prevalence of wheezing was almost twice as
high in homes that had pets at time of birth of
children.
Wheezing was assessed as the child has pre-
sented some skin allergy in the first year of life, as
well as the presence of mold or moist spots in homes
these children. Nonetheless, these variables did not
show significant risk factors of statistical point of view
to wheezing, since the prevalence ratio showed mini-
mal intervals of less than 1, as shown in Table 4.
Finally, we evaluated the wheezing for charac-
teristics related to breastfeeding, colds and contacts
with other people. It was found that the age group
Table 4: Assessment of prevalence as birth, vaccination, contact with animals and due to allergies and
mold
Variables Group Wheezing Not Wheezing RP IC95% p
f % f % Mín. Máx.
Cesarean childbirth Yes 17 42.5 16 40.0 0.60 0.38 0.94 0.09
No 6 15.0 1 2.5
Vaccines days Yes 18 46.2 16 41.0 0.66 0.38 1.13 0.25
No 4 10.3 1 2.6
Animal at birth Yes 9 22.5 1 2.5 1.92 1.24 2.97 0.01*
No 14 35.0 16 40.0
Animal currently Yes 8 20.0 4 10.0 1.24 0.73 2.11 0.44
No 15 37.5 13 32.5
Alergy at 1st year of life Yes 14 35.9 9 23.1 1.21 0.67 2.19 0.50
No 8 20.5 8 20.5
Mold in the home Yes 7 17.9 2 5.1 1.55 0.94 2.56 0.14
No 15 38,5 15 38,5
with wheezing showed exclusive breastfeeding within
the group not exceeding hissing, as the group had
wheezing and number of siblings living in the home
higher than the group without wheezing. It was found
also that the number of colds in the first year of life
was highest in the group of sibilants. However, none
of these variables showed a statistically significant
difference between groups. Only age was significant
that the infant has cooled for the first time: the aver-
age age that babies are cooled wheezing for the first
time was at 3 months, whereas it was not wheezing
at 6 months, suggesting, therefore, that cold is asso-
ciated with early wheezing, according to data detailed
in Table 5.
Table 5: Evaluation of breastfeeding as wheezing, colds and contacts with others
Variables Wheezing No Wheezing U p
MSTM ST
exclusive breastfeeding 4.86 3.94 3.65 2.37 159.00 0.44
Colds in 1st year 5.05 3.61 3.65 3.18 145.00 0.24
Age that has cooled (1st time) 3.14 2.58 6.35 3.69 90.50 0.00*
Number of brothers 1.23 1.63 0.88 1.21 160.50 0.45
Nº of household members 4.73 2.00 4.53 2.12 165.50 0.54
DISCUSSION
Wheezing is the main complaint in doctors
during infancy and in most cases related to bron-
chial hyperresponsiveness. Asthma and bronchioli-
tis are the most common causes of wheezing in
infants and children, respectively11. We aimed to
describe the risk factors for wheezing in infants in
the first year of life.
Because it hardly established recurrent
wheezing in infants shows distinct indices, ranging
between 10% and 43%. The lack of standardiza-
tion in the definition of wheezing, the type of study
and the age range of these studies may be the cause
of such variation12. In the present study, the preva-
lence of wheezing episodes during the first year of
life was 57.5% compared with studies done in the
city of Porto Alegre, Rio Grande do Sul, Brazil point-
ing its prevalence as 61%5.
In this research it was observed that there
was a predominance of male infants whistling as
has been shown by several researchers5-10, but cal-

Risk factors for recurrent wheezing in infants Journal of Human Growth and Development 2013; 23(2): 203-208
– 207 -
culated the prevalence ratio was not significant. The
reason for this gender difference is based on lower
airway caliber male relative to the female gender13,
this relationship, which is reversed as the child
reaches adolescence.
The “sizzle”, despite its decreasing incidence
with increasing age of the child, it is present
throughout childhood. Longitudinal studies showed
that during the first years of life the ‘early transient
wheezing’ is quite common14.
Infants who have a family history of
asthma2,6,15,rhinitis15 and allergic dermatitis have the
greatest chance to present episodes of wheezing in
the first 12 months of life, showing that heredity is
an important risk factor for wheezing and asthma
later2,5,6,10,12,13.
Genetic factors as well as environmental ex-
posure to allergens and not specific factors con-
tribute to the emergence of a complex network that
influences atopic diseases16.
The style and living conditions of the mother
during pregnancy have a relationship with the on-
set of wheezing in infants, such as maternal his-
tory of asthma and tobacco use during gestation17.
In our study, as in the study of Chong Neto et al.6,
it was found that constant exposure of infants to
tobacco in household environment after birth is not
associated with factors that increase the risk of
wheezing. However, Lima et al.5 indicated that uter-
ine exposure doubles the risk. Contrary to our study,
there is the research of Medeiros et al.2 who found
a significant relationship between passive smoking
in the household environment and not in maternal
smoking during pregnancy.
The presence of domestic animals at the time
of birth of the child, unlike the current presence of
animals, proved to be a risk factor for the onset of
wheezing in infants investigated, data consistent
with the findings of Chong Neto et al6.
Exclusive breastfeeding in the first months
of life is considered in some studies as a protective
factor for wheezing2,4,6,11,12,18, which was not con-
firmed in our study, that shows no significance re-
garding this factor. However, according to Hanson
and Korotkova Telemo19 breast milk stimulates the
development of the child’s immune system helping
in the prevention of allergic diseases.
The amount of colds in the first year of life
despite higher in the group of wheezing infants
showed no significant value, but the average age
that had been cold the first three months for
wheezing and six months for not whistling, pro-
posing that the lower the age at first episode of
flu, the greater the risk of the baby has wheezing
attacks in the future. These results are opposed
to studies of other researchers2,6, showing an as-
sociation between wheezing and more than six
colds in the first year of life.
Respiratory disorders in infants are an im-
portant issue investigated recently20, 21. The devel-
opment of this research enabled the achievement
of the goal initially traced, allowing to identify risk
factors for recurrent wheezing in infants smoking
during pregnancy, family history of asthma, rhinitis
and allergic dermatitis have pet at home at the time
of birth and age the first cold less than or equal to
three months of life. Further, it was found that the
prevalence is high.
CONCLUSION
Some risk factors in our study were similar
to those found in other studies, however, factors
such as male gender, presence of mold / mildew in
residence, age and number of colds in the first year
of life showed no statistically significant as in other
studies. Further studies are needed in different re-
gions of the country so you can have the knowl-
edge of the true prevalence of wheezing and knowl-
edge of risk factors that influence it.
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