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 Table of Contents  
Year : 2020  |  Volume : 7  |  Issue : 2  |  Page : 79-83

Risk factors for bronchiolitis

Department of Pediatrics, Karnataka Institute of Medical Sciences, Hubli, Karnataka, India

Date of Submission02-Feb-2020
Date of Decision28-Feb-2020
Date of Acceptance08-Mar-2020
Date of Web Publication10-Apr-2020

Correspondence Address:
Dr. Vinod H Ratageri
Department of Pediatrics, Karnataka Institute of Medical Sciences, Hubli - 580 021, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JPCC.JPCC_23_20

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Background: Bronchiolitis is a common acute respiratory illness with significant morbidity and mortality in children aged <2 years. Many risk factors have been proposed though none conclusively proven.
Objective: The objective of the study is to determine the risk factors for bronchiolitis in children aged <24 months.
Methodology: This was a retrospective study conducted at Karnataka Institute of Medical Sciences, Hubli, from July to September 2018 on children aged <24 months, with clinically diagnosed bronchiolitis considered as cases and age-matched children admitted during the same period for nonrespiratory causes as controls.
Results: Totally, 85 children and 91 controls were included in the study with a mean age at presentation being 5.5 months (interquartile range = 2–8 months) and male-to-female ratio of 1.42:1. The most common symptoms were cough (98.8%), fever (84.7%), cold (64.7%), hurried breathing (58.8%), chest indrawing (42.2%), and noisy breathing (35.3%). On univariate analysis, low socioeconomic status (SES), overcrowding, unimmunized status, exposure to pets, and birth by cesarean section (CS) were significant risk factors. On applying multiple logistic regression (odds ratio, 95% confidence interval), low SES, unimmunized status, exposure to pets, and birth by CS were found to be significant.
Conclusion: Low SES, partial/unimmunized status, exposure to pets, and birth by CS were deduced to be important significant risk factors for bronchiolitis.

Keywords: Bronchiolitis, infants, pets, risk factors, socioeconomic

How to cite this article:
Kulhalli P, Dakshayini J N, Ratageri VH, Shivanand I, Wari PK. Risk factors for bronchiolitis. J Pediatr Crit Care 2020;7:79-83

How to cite this URL:
Kulhalli P, Dakshayini J N, Ratageri VH, Shivanand I, Wari PK. Risk factors for bronchiolitis. J Pediatr Crit Care [serial online] 2020 [cited 2020 May 31];7:79-83. Available from: http://www.jpcc.org.in/text.asp?2020/7/2/79/282220

  Introduction Top

Bronchiolitis is an acute respiratory illness of importance that affects infants and young children and is one of the most common clinical conditions treated by practicing pediatricians worldwide. Children typically aged <2 years are affected.[1] Occurrence peaks in winter and rainy seasons. The incidence of bronchiolitis is estimated to range from 265/1000 infants to 16.4/100 children.[2] Mortality rate is approximately 2/100,000 infants and is higher in developing than developed countries.[3]

A number of risk factors and clinical findings have been proposed to predict the severity of disease in children with bronchiolitis. Host-related factors such as prematurity, low birth weight (LBW), age <6–12 weeks, chronic pulmonary disease, hemodynamically significant congenital heart disease, and immunodeficiency have been implicated.[4] Malnutrition, nonimmunization, and nonbreastfeeding were some significant risk factors for severe bronchiolitis. The other risk factors deduced in other studies include socioeconomic factors such as parental illiteracy, low SES, overcrowding, prelacteal feeds, and early weaning.[5] Environmental factors such as presence of older sibling and passive smoke exposure have been implicated.

However, there is a paucity of literature on risk factors for the development of bronchiolitis, in the Indian context, and hence, the present study was undertaken.


The aim of the study is to determine risk factors for bronchiolitis in children aged <24 months.

  Methodology Top

Study design

This was a retrospective study in children admitted to the Pediatrics Department, Karnataka Institute of Medical Sciences, Hubli, from July 2018 to September 2018, who satisfy the inclusion criteria.

Inclusion criteria

All children aged <24 months with clinically diagnosed bronchiolitis were enrolled in the study.[6] Children admitted during this period for nonrespiratory pathology who were <24 months old, with no prior history of bronchiolitis, were considered as controls.

Exclusion criteria

  1. Confirmed bronchopneumonia
  2. Children with chronic illness (cardiac, pulmonary, neurologic, chromosomal, or craniofacial comorbidities)
  3. Previously diagnosed with asthma.

The study was approved by the institutional ethical committee.

Demographic and risk factor data collected

The medical records of children included in this study were reviewed, and the information was collected in a predesigned Proforma.

The following demographic data were recorded: age in months, sex, delivery by normal or cesarean section (CS), premature birth (gestational age <37 weeks), and LBW (<2500 g); immunization status was categorized into two groups: group 1 “fully/completely immunized” and group 2 partial/unimmunized. Fully immunized defined as a receipt of six vaccines by 12 months of age as per the National Institute of Health and Family Welfare guidelines.[7] Socioeconomic class defined as per the Modified Kuppuswamy scale 2017;[8] malnutrition defined by the WHO for severe and moderate acute malnutrition as (I) weight for height/length <−3Z score and −2 to −3Z, respectively; (II) presence of visible severe wasting; (III) nutritional edema; (IV) mid-upper arm circumference of <115 mm, family history of asthma, allergies, history of bottle feeding, overcrowding,[9] and coexistence with pets.

Statistical analysis

The data were analyzed using R software version 3.1 (R Foundation for Statistical Computing, Vienna, Austria); a P ≤ 0.05 was accepted statistically significant. Simple associations were compared with Chi-square test as appropriate. Odds ratios with 95% confidence interval (CI) were calculated by risk assessment of Chi-square analysis, and logistic regression by the entry method was performed using variables found to be statistically different between two groups.

  Results Top

Totally, 85 children aged <24 months and 91 controls were included in the study. [Figure 1] shows the flowchart of selection of cases.
Figure 1: Selection of cases for the study

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The mean age at presentation was 5.5 months (median - 5 months; interquartile range - 2–8 months). The male-to-female ratio 1.42:1, with a male preponderance of 58.8% (n = 50) in the study group and 1.02:1 (n = 46) in the control group. Age at presentation in the order of frequency was <6 months (n = 57, 67.05%), 7–12 months (n = 25, 29.41%), and 13–24 months (n = 3, 3.5%), with P value being significant for under 6 months of age. Details are summarized in [Table 1].
Table 1: Comparison of sex and age of presentations between cases and controls

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The common clinical symptoms in the order of frequency were as follows: cough (n = 84, 98.8%), fever (n = 72, 84.7%), cold (n = 55, 64.7%), hurried breathing (n = 50, 58.8%), chest indrawing (n = 36, 42.4%), and noisy breathing (n = 30, 35.3%). However, stridor was not observed in any case. On examination, rhonchi in n = 54, 63.5%, and crepitations in n = 52, 61.2%, were also noted. Bilateral hyperinflation on the chest X-ray was seen in n = 77, 90.6%.

[Table 2] shows the risk factors for bronchiolitis. Low SES, overcrowding, incomplete immunization, exposure to pets, and birth by CS were the significant risk factors. However, preterm birth, LBW, maternal allergy, atopy, maternal diabetes/hypertension, malnutrition, family history of asthma, and bottle feeding showed no significant association as risk factors.
Table 2: Risk factors for bronchiolitis (n=85) - univariate analysis

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After application of multiple logistic regression analysis [Table 3] with the application of odds ratio with 95% CI, the results showed significance for lower SES, birth by lower segment CS, exposure to pets, and partial/incomplete immunization only.
Table 3: Multiple logistic regression analysis for risk factors for bronchiolitis

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  Discussion Top

Bronchiolitis is a common respiratory illness in pediatrics that causes acute inflammation, edema, necrosis of epithelial cells, increased mucus production, and inadequate oxygenation and could be potentially life-threatening.

This study aimed at assessing the risk factors for acute bronchiolitis. There was male preponderance identified in the study. As evidenced by literature, there is a greater incidence of bronchiolitis in boys.[5] The study by Bakalovic et al.[10] at Sarajevo University also stated the higher percentage of hospitalized male infants. This could be attributable to increased sensitivity of males to aeroallergens.[11]

The median age at presentation was 5 months. Similar to this, others have found a significant association between the age of <6 months and a higher risk of hospitalization and severe bronchiolitis.[4],[12] This is probably secondary to reduced immunity in early infancy toward viral infections.

In this study, of 13 risk factors initially considered, five risk factors namely low SES, overcrowding, exposure to pets, birth by CS, and incomplete immunization showed significance on univariate analysis. However, on application of multiple logistic regression analysis, four risk factors, such as low SES, birth by CS, exposure to pets, and incomplete immunization, showed significance.

Low SES was found as significant risk factor for bronchiolitis, similar to the study done by Díez Domingo et al.[13] Higher incidence of hospital admission due to respiratory infection in poor was found in study by Jansson et al.[14] The possible explanations could be that children from low SES are more vulnerable to air pollution, infection, nutritional deficiency, and numerous environmental hazards and possibly because disadvantaged mothers have less access to healthcare services.[15],[16] In a large-scale study done by Alvarez et al.[17] in Brazil, low SES was found as a major risk factor along with birth by CS.

Birth by CS was identified as a second major risk factor. Similar results were obtained by a study done at Denmark, where increased incidence of bronchiolitis and respiratory syncytial virus (RSV) infection was seen in CS born children aged <2 years.[18] Shang et al.[19] found almost double the incidence of bronchiolitis in children born by CS. The same findings were however refuted by Achten et al.[20] in 2015 and Hendaus et al.,[21] where no enhanced incidence was found. The possible analogy could be that CS or delivery without preceding labor may result in impaired immunity in newborn, leading to increased risk of early viral lower respiratory tract infections.[22]

Another significant variable in this study was exposure to pets in the house. However, studies have shown protection of exposed infants from bronchiolitis.[23] Others have reported that contact with pets either increases the risk or induces sensitization or protects against them or has no association at all.[24] Exposure to pets was implicated as risk factor in the study done by Malla et al.[25] in Nepal. Incidence was statistically higher in those exposed to pets as in the study by Nenna et al.[26] similar to the current study. Even with this, it is ridden with controversy regarding the correlation of pet exposure to bronchiolitis and hence needs more validation in the future studies.

RSV and influenza virus have been implicated as major pathogens in causation of bronchiolitis and targeting them has been stressed.[27] However, vaccination for them was not given in the present study group due to constraints. This, in addition to lack of cross-protection in these incompletely immunized patients, probably explains the enhanced incidence and its role as a major risk factor. In a study done by Das et al.,[28] similar results of nonvaccinated children having increased incidence of bronchiolitis in 55.55% of patients were seen.

The pros of this study were the inclusion of several modifiable risk factors and descriptive cases and controls; however, the limitation was, as it was a retrospective study and hence we did not have satisfactory access to variables being collected from control group.

We identified several risk factors for acute bronchiolitis such as low SES, partial/incomplete immunization, exposure to pets, and unindicated births by CS. This information would help public health authorities draw up effective preventive measures for bronchiolitis. Early identification and prevention of the same may help reduce the overall incidence. Due to dearth of studies on risk factors of bronchiolitis, this study explores novel factors to be considered for future research.

  Conclusion Top

Low SES, incomplete immunization, exposure to pets, and birth by CS were deduced to be the important significant risk factors for bronchiolitis.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Welliver RC. Review of epidemiology and clinical risk factors for severe respiratory syncytial virus (RSV) infection. J Pediatr 2003;143:S112-7.  Back to cited text no. 1
Muñoz-Quiles C, López-Lacort M, Úbeda-Sansano I, Alemán-Sánchez S, Pérez-Vilar S, Puig-Barberà J, et al. Population-based analysis of bronchiolitis epidemiology in Valencia, Spain. Pediatr Infect Dis J 2016;35:275-80.  Back to cited text no. 2
Holman RC, Shay DK, Curns AT, Lingappa JR, Anderson LJ. Risk factors for bronchiolitis-associated deaths among infants in the United States. Pediatr Infect Dis J 2003;22:483-90.  Back to cited text no. 3
Hall CB, Weinberg GA, Iwane MK, Blumkin AK, Edwards KM, Staat MA, et al. The burden of respiratory syncytial virus infection in young children. N Engl J Med 2009;360:588-98.  Back to cited text no. 4
Simoes EA. Environmental and demographic risk factors for respiratory syncytial virus lower respiratory tract disease. J Pediatr 2003;143:S118-26.  Back to cited text no. 5
American Academy of Pediatrics Subcommittee on Diagnosis and Management of Bronchiolitis. Diagnosis and management of bronchiolitis. Pediatr 2006;118:1774-93.  Back to cited text no. 6
Immunization Handbook for Medical Officers. Department of Health and Family Welfare, Government of India; 2008. Available from: http//www.mohfw.nic.in. [Last accessed on 2019 Nov 21].  Back to cited text no. 7
Singh T, Sharma S, Nagesh S. Socio-economic status scales updated for 2017. Int J Res Med Sci 2017;5:3264-7.  Back to cited text no. 8
World Health Organization. Household crowding. In: Housing and Health Guidelines. Geneva: World Health Organization; 2018. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535289/B. [Last accessed on 2019 Nov 21].  Back to cited text no. 9
Bakalovic G, Dzinovic A, Baljic R, Dizdar S, Selimovic A. Epidemiological features of bronchiolitis in the Pediatric Clinic of Clinical Center of Sarajevo University. Mater Sociomed 2015;27:154-7.  Back to cited text no. 10
Guilbert TW, Morgan WJ, Zeiger RS, Bacharier LB, Boehmer SJ, Krawiec M, et al. Atopic characteristics of children with recurrent wheezing at high risk for the development of childhood asthma. J Allergy Clin Immunol 2004;114:1282-7.  Back to cited text no. 11
Papenburg J, Hamelin MÈ, Ouhoummane N, Carbonneau J, Ouakki M, Raymond F, et al. Comparison of risk factors for human metapneumovirus and respiratory syncytial virus disease severity in young children. J Infect Dis 2012;206:178-89.  Back to cited text no. 12
Díez Domingo J, Ridao López M, Ubeda Sansano I, Ballester Sanz A. Incidence and cost of hospitalizations for bronchiolitis and respiratory syncytial virus infections in the autonomous community of Valencia in Spain (2001 and 2002). An Pediatr (Barc) 2006;65:325-30.  Back to cited text no. 13
Jansson L, Nilsson P, Olsson M. Socioeconomic environmental factors and hospitalization for acute bronchiolitis during infancy. Acta Paediatr 2002;91:335-8.  Back to cited text no. 14
Leem JH, Kim HC, Lee JY, Sohn JR. Interaction between bronchiolitis diagnosed before 2 years of age and socio-economic status for bronchial hyperreactivity. Environ Health Toxicol 2011;26:e2011012.  Back to cited text no. 15
Koehoorn M, Karr CJ, Demers PA, Lencar C, Tamburic L, Brauer M. Descriptive epidemiology of bronchioloits in a population based cohort. Pediatr 2008;122:1196-203.  Back to cited text no. 16
Alvarez AE, Marson FA, Bertuzzo CS, Arns CW, Ribeiro JD. Epidemiological and genetic characteristics associated with the severity of acute viral bronchiolitis by respiratory syncytial virus. J Pediatr (Rio J) 2013;89:531-43.  Back to cited text no. 17
Kristensen K, Fisker N, Haerskjold A, Ravn H, Simões EA, Stensballe L. Caesarean section and hospitalization for respiratory syncytial virus infection: A population-based study. Pediatr Infect Dis J 2015;34:145-8.  Back to cited text no. 18
Shang X, Liabsuetrakul T, Sangsupawanich P, Xia X, He P, Cao H. Elective cesarean delivery as a predisposing factor of respiratory syncytial virus bronchiolitis in children. J Med Assoc Thai 2014;97:827-34.  Back to cited text no. 19
Achten NB, Wu P, Bont L, Blanken MO, Gebretsadik T, Chappell JD, et al. Interference between respiratory syncytial virus and human rhinovirus infection in infancy. J Infect Dis 2017;215:1102-6.  Back to cited text no. 20
Hendaus MA, Alhammadi AH, Khalifa MS, Muneer E. Does cesarean section pose a risk of respiratory syncytial virus bronchiolitis in infants and children? Asian Pac J Trop Med 2014;7S1:S134-6.  Back to cited text no. 21
Moore HC, de Klerk N, Holt P, Richmond PC, Lehmann D. Hospitalisation for bronchiolitis in infants is more common after elective caesarean delivery. Arch Dis Child 2012;97:410-4.  Back to cited text no. 22
Custovic A, Simpson BM, Simpson A, Kissen P, Woodcock A; NAC Manchester Asthma and Allergy Study Group. Effect of environmental manipulation in pregnancy and early life on respiratory symptoms and atopy during first year of life: A randomised trial. Lancet 2001;358:188-93.  Back to cited text no. 23
Dharmage SC, Lodge CL, Matheson MC, Campbell B, Lowe AJ. Exposure to cats: Update on risks for sensitization and allergic diseases. Curr Allergy Asthma Rep 2012;12:413-23.  Back to cited text no. 24
Malla T, Poudyal P, Malla KK. Modifiable demographic factors that differentiate bronchiolitis from pneumonia in Nepalese children less than two years – A hospital based study. Kathmandu Univ Med J (KUMJ) 2014;12:175-80.  Back to cited text no. 25
Nenna R, Cutrera R, Frassanito A, Alessandroni C, Nicolai A, Cangiano G, et al. Modifiable risk factors associated with bronchiolitis. Ther Adv Respir Dis 2017;11:393-401.  Back to cited text no. 26
Behzadi MA, Leyva-Grado VH. Overview of current therapeutics and novel candidates against influenza, respiratory syncytial virus, and middle east respiratory syndrome coronavirus infections. Front Microbiol 2019;10:1327.  Back to cited text no. 27
Das PK, Saha JB, Basu K, Lahiri S, Sarkar GN. Some clinic-epidemiological aspect of bronchiolitis among infants and young children – A hospital based study. Indian J Public Health 2003;47:66-71.  Back to cited text no. 28


  [Figure 1]

  [Table 1], [Table 2], [Table 3]


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