Prospective Cohort Study on Infant Bronchiolitis

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Arvo building, auditorium F114, address: Arvo Ylpön katu 34.

Sari Törmänen
Photo: Jonne Renvall / University of Tampere

Doctoral defence of Lic.Med. Sari Törmänen

Prospective Cohort Study on Infant Bronchiolitis : The role of Toll-like receptors and allergy in the long-term outcome

The field of science of the dissertation is Paediatrics.

The opponent is docent Heikki Lukkarinen (University of Turku). Professor emeritus Matti Korppi acts as the custos.

The language of the dissertation defence is Finnish.

Risk factors for post-bronchiolitis asthma

Bronchiolitis is a lower respiratory tract infection caused by a virus and often leading to hospitalisation, especially in the youngest infants. Recurrent wheezing episodes are common in the years following the contraction of bronchiolitis, and long-term follow-up studies have shown that children infected as infants are at high risk of developing asthma. Established risk factors for post-bronchiolitis asthma include atopic predisposition, exposure to tobacco smoke in infancy, blood eosinophilia during bronchiolitis and rhinovirus as a causative agent of bronchiolitis. However, these risk factors do not fully explain the differences in individual outcomes. Especially innate immunity and genes regulating the immune responses seem to play  a role in the disease process. Toll-like receptors (TLRs) are innate immunity proteins, that recognise material foreign to host cells. Variation in the encoding genes may lead to attenuated function of TLRs and further, altered immune responses.

This study aimed to investigate the incidence of asthma and related allergic diseases at 11–13 years of age after bronchiolitis in infancy and to evaluate risk factors in early childhood and at preschool age that could have value in predicting the long-term prognosis. In addition, the aim was to evaluate the role of single nucleotide polymorphisms of TLR genes in the post-bronchiolitis asthma. The children that took part in this study were hospitalised for bronchiolitis under 6 months of age and the control visits have been arranged at 1.5, 5–7 and 11–13 years of ages.

The prevalence of asthma was 13.0% in the early teenage years after bronchiolitis in infancy, and means a two-fold asthma risk compared to the general school-aged child population. Maternal asthma was a significant early-life risk factor for post-bronchiolitis asthma and allergic rhinitis and skin prick test positivity were risk factors at preschool age. This study showed preliminary evidence that polymorphisms in TLR10 and TLR1 genes may increase the risk of post-bronchiolitis asthma in preschool age and in the early teenage years.

The dissertation is published in the publication series of Acta Universitatis Tamperensis; 2383, Tampere University Press, Tampere 2018. The dissertation is also published in the e-series Acta Electronica Universitatis Tamperensis; 1892, Tampere University Press 2018.

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