Prevalence of childhood cough in epidemiological studies ...

[Pages:9]medRxiv preprint doi: ; this version posted March 31, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in

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1 Prevalence of childhood cough in epidemiological studies: does it matter which 2 question we use?

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4 Authors: Maria Christina Mallet1,2, Rebeca Mozun1,3, Cristina Ardura-Garcia1, Philipp Latzin4, 5 Alexander Moeller5, Claudia E. Kuehni1,4

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7 Affiliations:

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1. Institute of Social and Preventive Medicine, University of Bern, Switzerland

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2. Graduate School for Health Sciences, University of Bern, Switzerland

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3. Graduate School for Cellular and Biomedical Sciences, University of Bern, Switzerland

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4. Paediatric Respiratory Medicine, University Children's Hospital Bern, University of

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Bern, Switzerland

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5. Division of Respiratory Medicine, University Children's Hospital Zurich and Children's

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Research Centre, University of Zurich, Switzerland

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16 Corresponding author: Prof. Dr. med Claudia E. Kuehni, Institute of Social and Preventive 17 Medicine, University of Bern, Mittelstrasse 43, 3012, Bern, Switzerland; email: 18 claudia.kuehni@ispm.unibe.ch

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NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.

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medRxiv preprint doi: ; this version posted March 31, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in

perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license .

33 ABSTRACT 34 We assessed how prevalence estimates of cough in 6-17-year-olds vary depending on the 35 question asked in the population-based Luftibus in the school (LUIS) study. 3427 parents 36 answered three different questions on cough. The prevalence of parent-reported cough 37 varied substantially depending on the question: 25% of parents reported cough without a 38 cold, 11% dry night cough and 5% that their child coughs more than other children. There 39 was only partial overlap with 3% answering yes to all questions. This suggests that the exact 40 question used to assess cough strongly affects prevalence estimates and must be taken into 41 account when comparing studies. 42 Words: 100/100

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medRxiv preprint doi: ; this version posted March 31, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in

perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license .

54 INTRODUCTION

55 Epidemiological studies often estimate prevalence of cough through parental 56 questionnaires. Cough is common in children and occurs as a physiological response during 57 upper respiratory tract infections, but frequent cough in the absence of an airway tract 58 infection is typical for chronic respiratory diseases such as asthma.[1] Different research 59 networks have developed specific questions to identify children with cough that exceeds the 60 normal expected physiological occurrence. The American Thoracic Society (ATS) 61 questionnaire asks if the child has "a cough even without having a cold".[2] The 62 International Study of Asthma and Allergies in Childhood (ISAAC) asks for "a dry cough at 63 night, apart from a cough associated with a cold or a chest infection"[3] and a questionnaire 64 developed in Southampton and used in several studies inquires if the child "coughs more 65 than other children".[4]

66 Most epidemiological studies conducted in the field of child respiratory health have only 67 included one of these cough questions basing the prevalence of cough on this single 68 question.[5-7] This has made it impossible to distinguish whether differences in prevalence 69 of cough between studies reflect regional variations, differences in study populations, 70 varying exposure to environmental risk factors, or if they result only from differences in the 71 wording of the question.

72 We used data from a large population-based study that included all three questions on 73 cough in the same questionnaire, to assess how prevalence of parent-reported cough in 74 children varies depending on the question that is used.

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medRxiv preprint doi: ; this version posted March 31, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in

perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license .

76 METHODS 77 We analysed data from LuftiBus in the School (LUIS), a cross-sectional population-based 78 study on respiratory health in schoolchildren, conducted in the canton of Zurich, 79 Switzerland, in 2013-2016.[8] Schools were dispersed across the entire canton and the 80 proportion of rural and urban schools and the area-based socioeconomic index of 81 participants was typical for the region.[8] Parents provided informed consent and 82 completed a questionnaire on respiratory symptoms of their child, including three different 83 questions about cough: "Does your child have a cough even without having a cold?" (cough 84 without a cold)[2], "In the last 12 months has your child had a dry cough at night, apart from 85 a cough associated with a cold or a chest infection?" (dry night cough)[3] and "Do you think 86 your child coughs more than other children?" (cough more than others).[4] We compared 87 the prevalence of cough as assessed using the three questions and constructed a Venn 88 diagram to describe the degree of overlap between parents' answers. We also stratified the 89 analyses for factors that could affect the prevalence of cough that are: current wheeze (as a 90 proxy for asthma), sex, and age group. We also assessed the duration of cough continuing 91 for more than three weeks and more than two months.

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93 RESULTS 94 Among 3870 participants from 37 schools, 3427 had completed parental questionnaires and 95 informed consent, and were included in the analysis. Median age was 13 years (range 6-17), 96 50% (1723) were girls and 8% (280) reported current wheeze (during the past 12 months).

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medRxiv preprint doi: ; this version posted March 31, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in

perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license .

97 The prevalence of cough differed substantially depending on the question asked. 872 (25%, 98 95% CI 24 ? 27%) parents reported cough without a cold, 390 (11%, 95% CI 10 ? 12%) dry 99 night cough and 158 (5%, 95% CI 4 ? 5%) answered that their child coughs more than other 100 children.

101 There was only partial overlap between the responses to the three cough questions (Figure 102 1A): 183 (5%) reported cough without a cold and dry night cough, but not coughing more 103 than others; 88 (3%) answered yes to all three questions and only 13 ( ................
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