The Liverpool Baby Breathing Study- The Cross-sectional and Longitudinal Assessment of Respiratory Symptoms and the Impact on Quality of Life in the First 22 Months of Life

Introduction. The Liverpool Baby Breathing Study (LBBS) is a longitudinal birth cohort study that investigates natural history of respiratory disease in preschool children in Merseyside. Merseyside has a high prevalence of risk factors for preschool respiratory disease. Preschool children in Liverpool have high rates of hospitalisation for asthma and bronchiolitis. Respiratory disease impacts on the quality of life (QoL) of infants and their families. The LBBS also assesses QoL impact on infants and their families, which makes the LBBS a novel study. Study Aims. The aims of this thesis are: 1. To create a profile of the infants and mothers enrolled in the LBBS and compare this to the eligible population. 2. To describe respiratory symptoms in the cohort using the Liverpool Respiratory Symptom Questionnaire (LRSQ) from birth until 22 months of age. 3. To determine the differences in LRSQ scores in infants exposed to various risk factors. 4. To determine the change in the LRSQ score over time and the variability in this change with exposure. 5. To validate the LRSQ in a longitudinal study. Methods. The LBBS uses the Liverpool Respiratory Symptom Questionnaire (LRSQ). Recruitment for the study was performed in the Liverpool Women’s Hospital (LWH). Eligible births were those infants who lived in Liverpool postcodes L1-38, spoke sufficient English and were cared for by their parents. Questionnaires were sent to participants by post or through an automated online emailing system. Recruitment rates and response rates were described using descriptive statistics. Sensitivity analysis was performed, comparing the drop out population’s exposure variables to the remaining cohort. The profile of the cohort was compared to the profile of eligible births in the LWH by χ2 analysis. Cross-sectional analysis compared those exposed to risk factors using χ2, Mann-Whitney U, Kruskal-Wallis analysis and Fisher’s Exact Test. The cross-sectional analysis of the LBBS was weighted to ensure the index of multiple deprivations (IMD) decile distribution of the cohort was comparable to the eligible births in the LWH. The longitudinal analysis of the LBBS was done using multi-level mixed effects models. The internal consistency of the LRSQ was assessed using Cronbach alpha coefficients. Results. 694 of the interested mothers (5.57% of all eligible births) consented to the study and completed the initial questionnaire. Attrition in the study was 44.0%, 60.4% and 63.0% at 10, 16 and 22 months. Mothers participating and retained in the LBBS were older, less deprived, more highly educated, breastfed more and smoked less in pregnancy than mothers of all eligible births. Infants were more likely to be of white or mixed ethnicity and born preterm than the eligible births. Cross-sectional analysis showed nursery attendance, being male, decreasing maternal age, decreasing maternal education, preterm birth, low birth weight, a family history of atopy and presence of other household children increased respiratory symptoms in the first 22 months of life. Breastfeeding and sharing a bedroom decreased respiratory symptoms. Longitudinally analysis found nursery attendance, being male, preterm birth, low birth weight, a family history of atopy and other household children increased respiratory symptoms over time. Breastfeeding, increasing gestational age and sharing a bedroom decreased respiratory symptoms over the first 22 months of life. Respiratory symptoms had a major impact on the QoL of both the infant and their families. There were unexpected and mixed results regarding the effect of smoke exposure on respiratory health in the LBBS. The LRSQ had acceptable to good internal consistency. Conclusion. The LBBS deployed the LRSQ using contemporary technology, and has been accessible to mothers in Liverpool across all deciles between 2012 through 2017. LBBS has validated use of the LRSQ in a longitudinal birth cohort. Breastfeeding had the greatest protective effect with a positive duration dependent dose-effect on respiratory symptoms and QoL. Nursery school attendance had the greatest deleterious effect on respiratory symptoms and QoL.