Epidemiology of childhood cough in Switzerland.

Mallet, Maria Christina (2023). Epidemiology of childhood cough in Switzerland. (Unpublished). (Dissertation, University of Bern, Division of Respiratory Medicine, Department of Pediatrics, University Children’s Hospital of Bern Faculty of Medicine)

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Background:
Cough has not only a protective role for the respiratory tract but it also serves as a warning sign of disease. However, cough significantly impacts the quality of life of children and their families, especially when it is persistent. It is thus fundamental to identify the underlying cause of cough and manage it accordingly. Even if cough is one of the most common respiratory symptoms in children, research on cough remains scarce and challenging. For instance, several cough questions exist, such as cough without a cold, dry night cough, and coughing more than other children, to identify children with cough exceeding the expected physiological occurrence. However, epidemiological studies usually include only one of these cough questions to assess cough prevalence. This makes it difficult to determine if differences in prevalence of cough between studies is due to differences in wording of the question or other factors such as environmental exposures. In addition, many children cough in the absence of wheeze and it is disputed whether these children may have a variant form of asthma. Only few population-based studies have compared whether children who have dry night cough without wheeze differ from those who wheeze, using both parent-reported information and measurable asthma traits. Furthermore, chronic cough has different underlying causes which vary across settings and age groups. Only few studies have assessed causes of chronic cough in children visiting healthcare settings. These studies had a small sample size or restricted age group, and most were single centre studies with limited generalisability of their findings. To classify cough into aetiologies, physicians often rely on clinical guidelines—these are usually based on expert opinions with some degree of overlap between diagnoses. Latent class analysis (LCA), a more objective statistical data-driven method, is increasingly used to distinguish phenotypes of respiratory problems such as wheeze and asthma. However, only few studies have applied LCA to children who cough, and these studies were population-based and mostly focused on asthma and wheeze with little emphasis on cough.

Aims:
The overall aim of my PhD thesis was to fill these research gaps and contribute to the epidemiological knowledge of childhood cough in Switzerland. More specifically, my aims were 1) to assess how the prevalence of cough varies depending on the cough question asked to parents and how answers to different cough questions overlap, 2) to compare how children who report dry night cough without wheeze differ from children who wheeze, 3) to assess the diagnostic evaluation and final diagnoses given to children referred to respiratory outpatient clinics for prolonged or recurrent cough, 4) to apply LCA to identify phenotypes of cough in a clinical population of children who cough without wheeze and lastly, 5) to assess whether the wearing of surgical facemasks during submaximal physical exercise affects gas exchange in children with exercise-induced symptoms.

Methods:
For aims 1 and 2, I used data from LuftiBus in the school (LUIS), a Swiss population-based study on respiratory health conducted among schoolchildren in the canton of Zurich. For aim 1, I compared the prevalence of three cough questions namely cough without a cold, dry night cough and coughing more than other children, and assessed how answers to these different questions overlap, and which factors affected the prevalence and overlap. I replicated the analysis in the Leicester Respiratory Cohort (LRC), a UK population-based study on respiratory health of children. For aim 2, I defined four mutually exclusive groups— ‘dry night cough alone’, ‘wheeze alone’, ‘wheeze and dry night cough’ and ‘neither wheeze nor dry night cough’. I assessed how these groups differed with respect to parent-reported symptoms, physiological measurements namely fractional exhaled nitric oxide (FeNO) and spirometry, healthcare use, and parent-reported physician asthma diagnosis and treatment. For aims 3, 4 and 5, I used data from the Swiss Paediatric Airway cohort, an observational multicentre study of children referred to respiratory outpatient clinics for the evaluation of common respiratory problems such as cough, wheeze, and exercise-induced symptoms. For aim 3, I extracted information on diagnostic investigations, final diagnoses proposed by paediatric pulmonologists, and treatment prescribed from outpatient records. For aim 4, I applied LCA to nine cough-related symptoms and characteristics reported by parents, to identify and describe cough phenotypes. I validated the identified cough phenotypes with respect to parental history, comorbidities, paediatric pulmonologists diagnoses, and respiratory prognosis after 1 year. For aim 5, I assessed oxygen saturation (SpO2) before and after exercise and results of capillary blood gas analysis measured immediately after exercise.

Results:
This thesis consists of five manuscripts (2 published, 1 under review, 1 submitted and 1 to be submitted). The main findings of each manuscript are summarised below:
Manuscript 1: There were large differences of up to five-fold in the prevalence estimates of cough based on the three questions, with only a partial overlap of positive answers to all three questions, in both LUIS and LRC. Prevalence estimates of all types of cough, as well as the overlap of positive answers between the cough questions was higher when the children reported wheeze.

Item Type:	Thesis (Dissertation)
Division/Institute:	04 Faculty of Medicine > Department of Gynaecology, Paediatrics and Endocrinology (DFKE) > Clinic of Paediatric Medicine 04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Social and Preventive Medicine (ISPM) 04 Faculty of Medicine > Department of Gynaecology, Paediatrics and Endocrinology (DFKE) > Clinic of Paediatric Medicine > Paediatric Pneumology
Graduate School:	Graduate School for Health Sciences (GHS)
UniBE Contributor:	Mallet, Maria Christina, Kühni, Claudia, Casaulta, Carmen
Subjects:	600 Technology > 610 Medicine & health 300 Social sciences, sociology & anthropology > 360 Social problems & social services
Language:	English
Submitter:	Beatrice Minder Wyssmann
Date Deposited:	16 Jun 2023 08:39
Last Modified:	11 Jan 2024 13:22
Additional Information:	PhD in Health Sciences (Epidemiology)
URI:	https://boris.unibe.ch/id/eprint/183464