Suchergebnisse

Electronic health records offer great potential for individual care, service improvement and, when collated, the health of the wider population. Datasets composed of these types of records have been invaluable to our understanding of risk factors for maternal and infant ill-health. However, a potential barrier to data quality in England is emerging where patients choose to opt out of sharing their information beyond the NHS. Focussing on maternity statistics, we will present the importance of population level health data for monitoring NHS services, and the potential consequences for patients of opting out. Evidencing the success of similar systems in Nordic countries, we argue that the English population must be better informed of the implications of opting out of sharing NHS data for research and the safeguards in place to protect patient information.

ABSTRACT
ObjectivesEmergency admissions for ambulatory care sensitive conditions (ACSCs) are thought to be preventable through preventive or early treatment interventions in primary care. However, evidence shows up to 70% of children with ACSCs admissions have underlying chronic conditions, suggesting that these admissions could be less amenable to primary care prevention than previously thought. We determined the extent to which primary care is involved in care by assessing primary care consultations before and after an emergency admission to hospital for an ACSC.
ApproachWe used a national general practice database (Clinical Practice Research Datalink) linked to hospital admissions data (Hospital Episode Statistics) and included children aged 0-19 years with emergency admissions for ACSCs or injury between 2000-2009. ACSCs were defined as acute infections (pneumonia and lower respiratory tract infections (LRTIs), dehydration and gastroenteritis (DGE), urinary tract infections (UTIs)), and asthma. We included injuries as a control group as we did not expect to see an increase in GP consultations for this group before emergency admission.
We calculated hospital admission rates by age, gender and area-level deprivation per 1,000 child-years and determined the proportion of children consulting their GP in the week before and week after emergency admission. We examined independent risk factors using zero-inflated negative binomial regression models.
ResultsWe extracted data for 1,664,555 children with 32,442 emergency admissions for ACSCs and 39,305 for injuries. There were clear socioeconomic gradients: LRTIs, UTIs and asthma were more prevalent in more deprived children, while rates for DGE and injuries were similar between deprivation quintiles. The majority of children with emergency admissions for ACSCs consulted their GP in the week before admission (range 58.3% (asthma) - 69.5% (LRTIs)), while 24.2% of children with injuries had a GP consultation. Children with ACSCs were more likely to consult their GP after discharge, with 37% (LRTIs) - 46% (UTI) of children consulting in the week after discharge, compared to 22% after injury admission. The proportion of children consulting their GP in the week before an emergency admission decreased. For LRTIs, this decreased from 71.7% in 2000 to 55.2% in 2009.
ConclusionThe majority of children consulted a GP both before and after an ACSC emergency admission. This suggest that the degree to which primary care can prevent ACSCs conditions in children might be less than previously thought. Further research is needed to determine which community or hospital based interventions, if any, can reduce ACSC emergency admissions.

IntroductionChild mortality is nearly twice as high in England as in Sweden. A comparison of mortality from potentially preventable causes could inform health system responses. This study focused on respiratory tract infection (RTI)-related deaths, amenable to healthcare interventions, and sudden unexpected deaths in infancy (SUDI), amenable to public health interventions.
Objectives and ApproachWe developed nationally-representative birth cohorts of singleton live births in 2003-2012 using a hospital admissions database in England and the Medical Birth Register in Sweden. Children were followed-up from 31st day of life until their fifth birthday via linkage to hospital admission and mortality records. We compared child mortality using Cox proportional hazards models to estimate hazard ratios (HR) for England versus Sweden for RTI-related mortality at 31-364 days and 1-4 years, and for SUDI mortality at 31-364 days. Models were adjusted for birth characteristics (gestational age, birthweight, sex, congenital anomalies), and socio-economic factors (maternal age and socio-economic status).
ResultsOf 3,928,483 children in England, there were 807 RTI-related deaths at 31-364 days (17% of all deaths in the age range), 691 deaths at 1-4 years (31%), and 1,166 SUDIs (24%) in England. Corresponding figures for 1,012,682 children in Sweden were 136 (18%), 118 (25%) and 189 (24%). Unadjusted HRs for RTI-related deaths in England versus Sweden were 1.50 (95% confidence interval: 1.25-1.80) at 31-364 days. Adjustment for birth characteristics reduced the HR to 1.16 (0.97-1.39), and for socio-economic factors to 1.11 (0.92-1.33). Corresponding figures for RTI-related mortality at 1-4 years were 1.58 (1.30-1.92), 1.32 (1.09-1.61) and 1.30 (1.07-1.59), respectively. Unadjusted HRs for SUDIs reduced from 1.59 (1.36-1.85) to 1.40 (1.20-1.63) after adjusting for birth characteristics, and to 1.19 (1.02-1.39) after adjusting for socio-economic factors.
Conclusion/ImplicationsHigher prevalence of adverse birth characteristics (such as prematurity, low birthweight, congenital anomalies) contributed to increased risks of RTI-related and SUDI mortality in England relative to Sweden. Therefore, preventive strategies should focus on maternal health and socio-economic circumstances before and during pregnancy to reduce RTI-related and SUDI mortality in England.

ABSTRACT
ObjectivesEngland has one of the highest child mortality rates in Western Europe, while Sweden has one of the lowest. These differences suggest that improvements in early life mortality should be achievable in England. However, policy makers need to know when in the life course to target interventions to prevent the largest number of deaths in early life, e.g. by addressing the prevalence of risk factors at birth (such as preterm birth or low birthweight), or improving the care of babies after birth. This study aims to compare child mortality in England and in Sweden using whole country birth cohorts based on linked administrative health databases in order to determine whether the disparities are driven by risk factors operating before or after birth.
ApproachWe created birth cohorts from a national birth register (Sweden) and a hospital admission database (England). These were linked to longitudinal hospital data and death registration data. All singleton live births for 2003-2012 were included and followed from birth up to five years. We compared mortality in England and in Sweden using Cox proportional hazard model with characteristics at birth (gestation, birthweight, gender, maternal age, congenital malformations), socio-economic status and country as covariates.
ResultsThe study cohort comprised 1,047,192 children in Sweden and 6,117,693 children in England. 2,820 of cohort children died in Sweden (0.3%) and 28,434 in England (0.5%).
Preliminary results showed that under-5 mortality was almost twice as high in England as in Sweden (5.1 deaths per 1000 live births, 95% confidence interval (CI): 5.0/1000-5.2/1000 vs 3.0/1000, 95% CI: 2.9/1000-3.2/1000). Mortality rates were 45% higher in England during infancy, but only 15% higher in early-childhood (1-4 years). Children with congenital malformations were at similar risk of death in England (33.9/1000, 95% CI: 32.9/1000-34.8/1000) as in Sweden (32.7/1000, 95% CI: 29.5/1000-35.8/1000). The prevalence of congenital malformations, however, was twice as high in England (5.1% vs 2.6%).
ConclusionsOur preliminary results suggest that the disparities in early-childhood mortality were partly driven by increased prevalence of congenital malformations in England relative to Sweden, as mortality rates within this group were comparable.
Individual-level data from birth cohorts constructed using linked administrative health databases enable comparing mortality among children with the same combinations of risk factors at birth. Such analyses can inform policy makers whether resources to prevent early-life mortality are most effectively targeted at improving the health of pregnant women, neonatal care, or supporting families with young children.

ObjectivesThe evidence-base for inter-related paternal and child health trajectories is not supported by linked, routinely collected administrative data in England. We conducted a scoping review to identify methods used globally for linking fathers and children in administrative data for public health research and map these methods onto dimensions of fatherhood.
ApproachWe searched PubMed, Scopus and Google/Google Scholar for articles published 2000-2020 from OECD countries that link fathers' and children's records in administrative data. Search terms included for example: "father" and "administrative data" or "record linkage". The exposures of interest were any demographic, health, or other characteristics of fathers during their offspring's childhood or prior to birth captured within administrative data. We included studies where paternal information came from fathers' linked records and if outcomes were related to child health and development (e.g. educational attainment, behavioural outcomes, hospital admissions) measured before 18 years of age.
ResultsWe identified 77 studies that quantified the association between paternal exposures and child health and development outcomes, using linked administrative data on fathers and their children. Four methods have been used globally to link fathers and children across vital statistics, health, social care, education, and criminal justice records. These methods are based on personal identity numbers (PINs), address or household identifiers, information from birth registrations, or health claims. We mapped what we can learn from these different linkages to dimensions of fatherhood identified through a conceptual framework. For example, for the linkage method based on address/household identifiers, co-residency may be used as a proxy for all dimensions of paternal involvement. However, substantial assumptions are needed when using linkage methods as proxies for paternal involvement.
ConclusionIn many settings, changes in practice (such as recording fathers' National Health Service numbers on hospital birth notifications in England) are required to facilitate linkage of father-child health data at the population level. This would help advance fatherhood research and enable targeted service offers to new fathers.

ABSTRACT
ObjectivesWe aimed to compare prevalence rates of complex congenital anomalies (CCAs) in the first two years of life in England and Scotland using two published CCA diagnosis code lists (phenotypes) developed to identify children who require high levels of healthcare.
ApproachWe developed birth cohorts of singleton, hospital live births between 1998-2011 using birth registration, hospitalisation and mortality register datasets from England (n=8,157,213) and from Scotland (n=731,377) from. Children were followed up until 2 years of age.
We compared prevalence rates of congenital anomalies using two code lists developed to identify CCAs: a UK chronic condition code list developed by Hardelid et al. and a US medical complexity code list developed by Feudtner et al. Children were classified as having a CCA if a diagnosis code was included in any admission during follow-up as a primary or subsidiary diagnosis.
To assess the level of healthcare attention required, we compared the proportion of children who had at least one re-admission to hospital in the first two years of life.
ResultsRates of CCAs in England and Scotland were higher using the Hardelid phenotype (2.8% for both countries) than when using the Feudtner phenotype (1.8% in England and 1.5% in Scotland). Rates of CCAs increased in both England and Scotland between 1998 and 2011. The increase was more notable using the Hardelid phenotype (37.2% and 20.2%, in England and Scotland, respectively) compared to the Feudtner phenotype (35.6% and 13.0%). Prevalence rates using the Hardelid phenotype were similar to EUROCAT figures. The proportion of children with at least one re-admission to hospital was higher in the Feudtner code list (69.2% in England and 84.8% in Scotland), than for Hardelid's code list (67.9% and 72.0% in England and Scotland, respectively). The proportions of children with any of the CCA phenotypes were higher than compared to children without CCAs (24.4% in England and 25.8% in Scotland).
ConclusionPrevalence of CCAs and associated hospital use vary depending on choice of CCA code list. Our findings suggest that Feudtner's code list identifies children with higher level of healthcare needs. The impact of coding methods for defining CCAs in administrative hospital records should be explored and externally validated when comparing prevalence of CCAs and associated hospital use between countries.
The impact of coding method for defining CCAs in administrative hospital records should be explored and externally validated when comparing prevalence and admission rates between countries.

ABSTRACTObjectiveAcute respiratory infections (ARI) including bronchiolitis, pneumonia and influenza are a major cause of hospital admissions in children worldwide. Linkage of administrative health datasets provides a platform to investigate temporal and seasonal trends in large populations over many years. We examined the similarities and differences in ARI admissions using linked datasets in Western Australia and England. ApproachThrough the availability of common data items in each jurisdiction, identical coding and data cleaning principles were applied to both datasets. Hospital admissions for ARI in children aged <5 years between 2000 and 2012 were identified using International Classification of Diseases diagnosis codes. Admission rates per 1000 child-years by age, gender and admission year were calculated in each jurisdiction. A total population birth cohort was available in Western Australia and the denominator was person time at risk whereas for England, all hospitalisations were used with the mid-year population as the denominator. ResultsThe overall incidence of ARI was 18.3/1000 child-years in Western Australia and 14.4/1000 in England. In both countries, the highest incidence of ARI was observed in infants (47.9/1000 child-years in Western Australia and 42.1/1000 child-years in England). Bronchiolitis was the most common primary diagnosis in infants in both countries, accounting for 79.7% of ARI admissions in Western Australia and 78.3% in England. The most common primary diagnosis in 1-4 year olds was unspecified lower respiratory tract infections in England (48.8% of ARI admissions in this age group) and pneumonia in Western Australia (43.9% of ARI admissions in 1-4-year-olds). The annual incidence rate for ARI hospitalisations declined in Western Australia from 2000 to 2006 and since remained steady. ARI admission rates increased in England throughout the study period. Admission rates across all age groups were 1.1-1.5 times higher in boys than girls in both countries. ConclusionThe availability of similar datasets in two economically similar countries in different hemispheres has afforded the opportunity to characterise and compare the epidemiology of paediatric respiratory infections over a 13 year period. Future analyses will allow us to assess differences in coding practices, seasonality and risk factors such as socio-economic deprivation and prematurity. Furthermore the availability of linked laboratory data for respiratory pathogens in each jurisdiction will allow for comparisons of pathogen-specific epidemiology and the impact of universal vaccination programs.

ObjectivesWe provide a national overview of survival to primary school and recorded special educational needs (SEN) provision among children with hospital identified major congenital anomalies (MCAs) born in England. We also report changes before and after government reform of SEN in 2014.
MethodsWe created a cohort of 6,180,400 singleton children born in England between 1 September 2003 and 31 August 2013 using linked administrative health and education records (from the 'ECHILD' database). MCAs were identified using hospital admission and mortality records during infancy. We used at least one record of SEN in state-school records as a proxy for SEN provision. We quantified: survival to age 5 using Kaplan-Meier survival analysis; the prevalence of recorded SEN during primary school Years 1 to 6; and the difference in proportion of children with recorded SEN in Year 1 before and after the 2014 government SEN reforms.
ResultsChildren with any MCA had 5-year survival rates of 95.1% (95% confidence interval, CI, 95.0, 95.2), compared with 99.7% (95% CI 99.7, 99.7) among children without a MCA. 41.5% (75,202/181,328) of children with an MCA attending state-school between Year 1 and 6 had any recorded SEN compared with 25.6% (1,282,979/5,008,624) of children without a MCA. Of the 12 system-specific MCA subgroups, children with chromosomal, nervous system and eye anomalies had the largest prevalence of recorded SEN. The prevalence of recorded SEN decreased by 4.9% (95% CI -5.3, -4.4) for children with any MCA compared with a reduction of 4.3% (95% CI -4.4, -4.2) for children without a MCA, when comparing pupils in Year 1 before and after 2014.
ConclusionRecorded SEN among children with hospital identified MCAs was markedly higher than for those without MCAs, however more than half had no recorded SEN. Our findings suggest government reform in 2014 reduced SEN provision for children with MCAs.

IntroductionInappropriate antibiotic prescribing, such as that for viral illness, is common in primary care. This is of growing interest given concerns around antimicrobial resistance and harms associated with unnecessary treatment; however, current data limitations have hindered population-based estimates of the proportion of community-prescribed antibiotics attributable to common respiratory viruses.
Objectives and ApproachTo estimate the proportion of antibiotics prescribed in primary care to young children attributable to common respiratory viruses, including respiratory syncytial virus (RSV), influenza, human metapneumovirus (HuMPV) and parainfluenza. We leveraged two unique sources of comprehensive, linked population-based administrative data on dispensed antibiotic prescriptions and laboratory tests for respiratory viruses for all Scottish children (<5 years). We fit time series negative binomial models to predict weekly antibiotic prescribing rates from positive viral tests rates for the period April 1, 2009 through Dec 27, 2017. Using linked demographic and hospitalization data, we stratified our analysis by age, presence of high-risk chronic medical conditions, and antibiotic class.
ResultsWe included data on over 6 million antibiotic prescriptions among nearly 800,000 children. An estimated 6.9% (95% CI: 5.6,8.3), 2.4% (1.7,3.1), and 2.3% (0.8,3.9) of prescribed antibiotics were attributable to RSV, influenza and HuMPV, respectively. RSV was consistently associated with the highest proportion of antibiotics prescribed across all analyses but particularly among children without chronic conditions [4.30% (3.19, 5.41)] and for amoxicillin [8.10% (6.43, 9.76)] and macrolide prescriptions [7.65% (6.14, 9.16)].
Conclusion / ImplicationsNearly 14% of antibiotics prescribed to Scottish children in this study were attributable to common viral pathogens such as RSV for which antibiotics are not recommended. This highlights clear targets for antibiotic stewardship programs and suggests antibiotic prescribing could be reduced once an RSV vaccine is introduced.

ABSTRACTObjectivesThis study aims to describe the burden of respiratory syncytial virus (RSV) in children <5 years of age on secondary care in England using linked laboratory surveillance and hospital admissions databases. We will compare our results with previous estimates of the burden of RSV in secondary care based on statistical modelling techniques.
ApproachNational laboratory surveillance data was probabilistically linked to the Hospital Episode Statistics (HES) database for children aged <5 years in England from 01/08/2010 to 31/07/2012. Linkage was based on NHS and hospital number, date of birth, sex and post code. Only records where the laboratory test was within one week of hospital admission were included. Using the linked data, we estimated the probability of a respiratory hospital admission being related to RSV based on patient characteristics, calendar week and diagnostic coding. We used these probabilities to estimate the national incidence of RSV-associated hospital admissions. Admission rates were calculated by age group (<1 year, 1-4 years) using Office for National Statistics (ONS) mid-year population estimates.
ResultsThere was an average of 11,289 RSV-positive laboratory records per year during the study period. Preliminary results indicate that 75% of RSV-positive laboratory records linked to a hospital admission. 92% of linked hospital admissions occurred between November and March each year. 76% of the linked hospital admissions were in children aged <1 year. There were significant differences in coding of RSV-associated hospital admissions by age, and over two-thirds of RSV-associated hospital admissions did not have a primary diagnosis indicating RSV as the cause of disease. We will present results on the number of linked hospital admissions, unlinked hospital admissions potentially caused by RSV and the total estimated number of RSV-associated hospital admissions, stratified by age, calendar week and primary diagnosis.
ConclusionThis study is the first to link laboratory and hospital data for RSV in England, and therefore the first to describe laboratory-confirmed RSV-associated hospital admissions on a national scale. Our approach to estimate the national incidence of admissions based on developing probability weights from a smaller, linked sample has applications not just for RSV but for other seasonal infections. In addition, with a World Health Organization (WHO) consultation last year estimating that an RSV vaccine will be available commercially within 5-10 years, the results of this study can be used in mathematical models of potential vaccine strategy, contributing to the identification of optimal target groups for a potential licensed vaccine.

Introduction & BackgroundEvidence is mounting that children's physical environment (e.g. in and around the home, school, and neighbourhood) is critical for their long-term health and education. Early life exposure to factors such as indoor and outdoor air pollution, or a lack of access to greenspaces are associated with the development of long-term health conditions such as asthma or mental health problems. Local and central government in England are implementing numerous policies to improve air quality and housing, and mitigate climate change. Further, England has seen large scale changes to local service provision (including childcare and libraries) due to austerity policies and the COVID-19 pandemic. Currently, there is no national, linked data resource for England that allows research into how the local environment impacts children's health and education.
Objectives & ApproachThe Kids' Environment and Health Cohort will be a new, linked national data resource for England currently being developing by researchers from UCL, London School of Hygiene and Tropical Medicine, London School of Economics and Political Science, Brock University, and City, University of London in collaboration with the Office for National Statistics (ONS), and funded by Administrative Data Research-UK (ADR-UK). The Kids' Environment and Health Cohort will be a de-identified and annually updated national birth cohort of all children born in England from 2006 onwards – around 10.5 million children until 2023. The cohort will be constructed using linked administrative data from vital registration (live and stillbirth, and death registration), Census (housing and socio-economic indicators), health (hospital contacts, mental health referrals, and community dispensing data), and education (key stage results, special educational needs, absenteeism). Environmental exposure data can be securely linked to the Cohort via longitudinal residential unique property reference numbers (UPRNs) and postcodes from the Personal Demographic Service, and school location from education records.
Relevance to Digital FootprintsThe Kids' Environment and Health Cohort will, for the first time, link health, education, Census and environmental data at national level in England. It will allow researchers to integrate data on local environments, including physical characteristics (such as temperature, building energy efficiency, or greenspace access) or the social environment (including proximity to food outlets, or services like libraries) with individual level data on health and education outcomes in children. This will be done using the ONS's 5 safes framework, ensuring highest standards of data security and confidentiality.
ResultsThe Kids' Environment and Health Cohort will be constructed using administrative datasets, including national linked vital statistics, health, education and Census data from multiple data providers (ONS, NHS England and Department for Education), combined with small-area level environmental data for England. Together, these datasets allow detailed analyses of the impact of environmental exposures on health and education outcomes in children, with robust confounder adjustment. The Kids' Environment and Health Cohort will be made available in a de-identified format in the ONS Secure Research Service (SRS).
Conclusions & ImplicationsThe Kids' Environment and Health Cohort will provide researchers secure access to a national data resource integrating environmental and administrative health and education data, for child public health research.

ABSTRACT
ObjectivesHigher rates of infant mortality in the UK than in the Nordic countries are partly explained by wider socio-economic disparities in the UK. We examined the extent to which low birth weight mediates the association between socioeconomic status (SES) and infant mortality using causal mediation analysis. We used cohorts of live births identified in administrative hospital data for the whole of Scotland and Denmark to explore the contribution of prenatal factors, represented by low birth weight, to differences in infant mortality between the two countries.
ApproachWe included live-born children born in Denmark (n=1,432,205) and Scotland (n=1,427,163) from 1981-2004. Follow up was to 12 months of age. Information on deaths in first year of life was obtained through linkage with cause of death registers. We determined the effect of socioeconomic status on all cause infant mortality by comparing the highest and lowest quintiles of area-based deprivation (based on Carstairs score in Scotland) or level of maternal education in Denmark. Causal mediation analysis was used for survival outcomes with adjustment for maternal age at birth, sex, birth year of the child, and records indicating congenital malformation.
ResultsDuring the follow-up, there were 8,158(0.57%) deaths in Denmark and 8,271(0.58%) deaths in Scotland. Comparing with the very high SES group, the overall hazard ratios of death for each SES quintile (starting with the lowest) compared with the highest SES quintile were 1.58(95% Confidence interval: 1.47-1.71), 1.40(1.32-1.49),1.25(1.20-1.30), 1.11(1.09-1.14) in Denmark, and 1.50(1.36-1.65),1.35(1.25-1.45),1.22(1.16-1.28),1.10(1.08-1.13) in Scotland. The proportions of excess infant deaths mediated through low birth weight (starting with the lowest) compared with the highest SES quintile were 54.7%, 52.1%, 49.5%, 46.9% in Denmark, and 26.0%, 23.9%, 22.0%, 20.1% in Scotland.
ConclusionOur result suggests that SES has similar effects on infant mortality in Denmark and Scotland but more of the effect of SES on infant mortality is mediated through low birth weight in Denmark. Public health preventive strategies for infant mortality in both countries need to address prenatal risk factors for low birth weight. The substantial direct effects of SES on infant mortality seen in Scotland, which were not mediated through low birth weight, may be explained by other birth characteristics or could reflect persisting SES disparities in the care of infants after birth.

ObjectiveTo estimate the association between household tenure and the odds of hospital admission for acute lower respiratory tract infections (LRTI) in children under age 2 years.
MethodsWe developed a birth cohort of all singleton children born in Scotland 2010-2012, using linked birth registration records and maternal Census 2011 data. Further linkage to hospital admission records provided information on acute LRTI (pneumonia, bronchitis, bronchiolitis, influenza, unspecified LRTI) admissions in children aged less than 2 years. Using logistic regression models, we estimated the association between housing tenure at birth (owned, social rented, private rented/lives rent free) with odds of hospital admission for LRTI before and after adjustment for parental occupational class (household reference), family type and highest qualification level.
ResultsFrom the cohort of all 174,279 births in 2010-2012, 84.1% linked to a maternal census record. Children whose parents were married or had a UK-born mother were more likely to link to a Census record. In the final linked cohort of 141,336 children, 7,486 (5.3%) were admitted to hospital for one or more LRTI during the 2 years of follow up. We found an association between housing tenure and LRTI admissions, with children residing in social rented, compared to owned housing having higher odds of an LRTI admission, OR: 1.40 (1.32-1.47); and children living in private rented/rent free housing, compared to owned, OR: 1.18 (1.11-1.26). After adjustment for household socioeconomic circumstances, these estimates attenuated to OR: 1.18 (1.11-1.27) and OR: 1.10 (1.03-1.18) respectively.
ConclusionAfter accounting for household socioeconomic circumstances, children living in social and private tenured accommodation, compared to children living in owned accommodation were more likely to be hospitalised for an acute LRTI during the first 2 years of life. Further research to understand the contribution specific housing circumstances make to inequalities in LRTI hospitalisations early in life is needed.

INTRODUCTION: Respiratory tract infections (RTIs) are the most common reason for hospital admission among children <5 years in the UK. The relative contribution of ambient air pollution exposure and adverse housing conditions to RTI admissions in young children is unclear and has not been assessed in a UK context. METHODS AND ANALYSIS: The aim of the PICNIC study (Air Pollution, housing and respiratory tract Infections in Children: NatIonal birth Cohort Study) is to quantify the extent to which in-utero, infant and childhood exposures to ambient air pollution and adverse housing conditions are associated with risk of RTI admissions in children <5 years old. We will use national administrative data birth cohorts, including data from all children born in England in 2005-2014 and in Scotland in 1997-2020, created via linkage between civil registration, maternity and hospital admission data sets. We will further enhance these cohorts via linkage to census data on housing conditions and socioeconomic position and small area-level data on ambient air pollution and building characteristics. We will use time-to-event analyses to examine the association between air pollution, housing characteristics and the risk of RTI admissions in children, calculate population attributable fractions for ambient air pollution and housing characteristics, and use causal mediation analyses to explore the mechanisms through which housing and air pollution influence the risk of infant RTI admission. ETHICS, EXPECTED IMPACT AND DISSEMINATION: To date, we have obtained approval from six ethics and information governance committees in England and two in Scotland. Our results will inform parents, national and local governments, the National Health Service and voluntary sector organisations of the relative contribution of adverse housing conditions and air pollution to RTI admissions in young children. We will publish our results in open-access journals and present our results to the public via parent groups and social media and on the PICNIC website. Code and metadata will be published on GitHub. ; publishedVersion ; Peer reviewed

INTRODUCTION: Respiratory tract infections (RTIs) are the most common reason for hospital admission among children <5 years in the UK. The relative contribution of ambient air pollution exposure and adverse housing conditions to RTI admissions in young children is unclear and has not been assessed in a UK context. METHODS AND ANALYSIS: The aim of the PICNIC study (Air Pollution, housing and respiratory tract Infections in Children: NatIonal birth Cohort Study) is to quantify the extent to which in-utero, infant and childhood exposures to ambient air pollution and adverse housing conditions are associated with risk of RTI admissions in children <5 years old. We will use national administrative data birth cohorts, including data from all children born in England in 2005-2014 and in Scotland in 1997-2020, created via linkage between civil registration, maternity and hospital admission data sets. We will further enhance these cohorts via linkage to census data on housing conditions and socioeconomic position and small area-level data on ambient air pollution and building characteristics. We will use time-to-event analyses to examine the association between air pollution, housing characteristics and the risk of RTI admissions in children, calculate population attributable fractions for ambient air pollution and housing characteristics, and use causal mediation analyses to explore the mechanisms through which housing and air pollution influence the risk of infant RTI admission. ETHICS, EXPECTED IMPACT AND DISSEMINATION: To date, we have obtained approval from six ethics and information governance committees in England and two in Scotland. Our results will inform parents, national and local governments, the National Health Service and voluntary sector organisations of the relative contribution of adverse housing conditions and air pollution to RTI admissions in young children. We will publish our results in open-access journals and present our results to the public via parent groups and social media and on the PICNIC website. Code and metadata will be published on GitHub.