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Test tubes in a lab

Thesis examines the factors associated with respiratory tract infections and the development of asthma in early life

We may be able to impact immunological responses in ways that will decrease the morbidity of respiratory infections in early childhood and even prevent the development of asthma, claims Eija Bergroth, Lic Med, in her study on risk factors, causes, and prognosis of respiratory tract infections among young children. For example, having a dog around an infant might benefit the child’s early immune development. In her study, children hospitalised for bronchiolitis caused by rhinovirus type C had the highest risk for the use of asthma control medication later in life.

Cord blood cytokines and animal contact are associated with respiratory infections during the first year of life

Resistance against foreign pathogens is developed from different functions of many cells and other mediators of the immune system. Resistance changes and develops throughout life. Differences can already be seen in the functions of newborns’ immune systems.

Cord blood samples were collected after each child was born. The ability of cord white blood cells to produce different cytokines, or proteins that signal cells in inflammatory and immune reactions, was compared to the reported frequency of respiratory tract infections and symptoms. Higher cord blood interleukin-5 and interferon-γ production were associated with fewer weeks of middle ear infections. A positive association occurred between tumour necrosis factor-α production and such ear infections.

Various environmental factors affect our immunological responses. In the present study, children with dogs were healthier (i.e., had fewer symptoms and infections) than children with no dogs. They also had less frequent ear infections and needed fewer antibiotics than their counterparts without dogs. Contact with cats demonstrated a less significant impact on the frequency of respiratory infections and symptoms.

Over 1,000 children born to mothers from mainly rural environments in Austria, Finland, France, Germany, and Switzerland participated in the birth cohort study PASTURE or its Finnish extension the LUKAS study. The children were born from September 2002 to May 2005. Their respiratory symptoms, infection frequencies and contact with dogs and cats during their first year were collected in weekly diaries.

Risk of asthma after bronchiolitis depends on viral cause of the infection

Bronchiolitis is a viral respiratory tract infection. It is one of the most common reasons for hospitalisation among young children. Bronchiolitis is also associated with the development of childhood asthma.

In this study, 47% of children hospitalised for rhinovirus bronchiolitis used asthma control medication four years after the infection. This use was more frequent than that in children hospitalised for respiratory syncytial virus bronchiolitis (15%) or bronchiolitis caused by other viruses (26%). The use of asthma medication was especially common among children who had bronchiolitis caused by rhinovirus type C, a history of atopic eczema and fever during hospitalisation. Based on the results and Bergroth’s thesis, the risk of developing asthma later in childhood is not the same for all the children hospitalised for bronchiolitis. Different treatment and follow-up strategies are needed depending on the cause of the infection. However, current treatment guidelines do not yet recommend diagnostic testing to determine the cause.  

In total, 408 children hospitalised for bronchiolitis at younger than two years old were enrolled in the MARC-30 Finland study. The children were hospitalised during winter months from 2008 to 2010 in Kuopio, Tampere and Turku University hospitals. The use of asthma control medication was examined at 12 and 24 months after bronchiolitis hospitalisation.

Based on the results of this research, having dogs while a child is in their infancy might benefit the child’s early immune development and, for example, decrease the respiratory tract infection frequency in early childhood.  Children with rhinovirus type C might be a good target for future asthma prevention studies.

The doctoral dissertation of Eija Bergroth, Lic Med, entitled Predictive Factors for Respiratory Infections and Post-Bronchiolitis Asthma in Early Childhood will be examined at the Faculty of Health Sciences. The opponent in the public examination will be Professor Minna Kaila of the University of Helsinki, and the custos will be Docent Sami Remes of the University of Eastern Finland. The public examination will be held in Finnish at Kuopio Campus and online on 4 September 2020 starting at 12 noon.

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Bergroth, Eija. Predictive factors for respiratory infections and post-bronchiolitis asthma in early childhood