The epidemiology of injuries in epilepsy and attention deficit-hyperactivity disorder (ADHD) in children and young people using the Clinical Practice Research Datalink (CPRD) and linked data

Background\ud \ud Injuries are a leading cause of morbidity and mortality in children and young people (CYP) throughout the world and in the UK. Detailed estimates of the risk of specific injuries, namely fractures, thermal injuries and poisonings, are not available for CYP with specific medical conditions, such as epilepsy or attention deficit-hyperactivity disorder (ADHD) in the English primary care population. To date there has been no description of the recording of ADHD by general practitioners (GPs) in English primary care according to people’s area-level social deprivation and strategic health authority (SHA) region.\ud \ud Objectives\ud \ud 1. To define a cohort of CYP with epilepsy from the UK primary care population.\ud 2. To estimate the risk of specific injuries, namely fractures, thermal injuries and poisonings in CYP with epilepsy compared to CYP without epilepsy.\ud 3. To define and describe the cumulative administrative prevalence of ADHD in CYP in English primary care overall and by age, sex, SHA region, deprivation and calendar time.\ud 4. To estimate the risk of specific injuries, namely fractures, thermal injuries and poisonings in CYP with ADHD compared to CYP without ADHD.\ud \ud Methods\ud \ud \ud This thesis describes work conducted using a large primary care dataset (the Clinical Practice Research Datalink (CPRD)) containing GP medical records and, for a proportion, linked hospital records from the hospital episodes statistics (HES) database. Firstly, the CPRD was used to define a cohort of CYP with epilepsy and CYP without epilepsy. The GP medical records for this cohort were used to estimate the risk of fractures, thermal injuries and poisonings, in CYP with epilepsy compared to CYP without epilepsy. The rates of injuries were estimated by age and sex. For a proportion of people in this study, the effect on estimates of using linked hospital medical records in addition to the GP medical records was evaluated. Secondly, the administrative prevalence of ADHD recorded by GPs was defined for CYP in England by identifying a cohort of CYP in the CPRD with GP medical records linked to hospital medical records. The cumulative administrative prevalence of ADHD was estimated overall and by age, sex, SHA region, deprivation and calendar time. Thirdly, the GP medical records and linked hospital medical records for the cohort of CYP with ADHD was used to estimate the risk of fractures, thermal injuries and poisonings, in CYP with ADHD compared to CYP without ADHD. The rates of injuries were estimated by age, sex and deprivation.\ud \ud Findings\ud \ud CYP with epilepsy are at greater risk of fractures, thermal injuries and poisonings compared to CYP without epilepsy. In CYP with epilepsy the incidence of fractures is 18% higher, thermal injuries is 50% higher and poisonings 147% higher than in CYP without epilepsy, with the increased risk being restricted to medicinal poisonings. Among young adults with epilepsy, aged 19 to 24 years, the incidence rate of medicinal poisoning is four-fold that of the general population of the same age. Using GP medical records and linked hospital medical records may improve the ascertainment of injuries. For example, if hospital medical records are used in addition to GP medical records to ascertain femur fractures, a further 33% of fractures may be ascertained compared to using GP medical records alone. In comparison, if hospital medical records were used without GP medical records, 10% of femur fractures may not be ascertained. However, this increased ascertainment of injuries is unlikely to alter the estimates of risk of injuries in people with epilepsy when compared to people without epilepsy (e.g. risk of long bone fractures: using hospital and GP medical records, hazard ratio (HR)=1.25 (95% confidence interval (95%CI) 1.07 to 1.46) vs. using GP medical records alone, HR=1.23 (95%CI 1.10 to 1.38)).\ud The administrative prevalence of ADHD in CYP aged 3 to 17 years old in English GP medical records is 0.88% (95% confidence interval (95%CI) 0.87 to 0.89). The prevalence of ADHD recorded by GPs is around five times greater in males than in females. The administrative prevalence of ADHD appears to increase with age, with the lowest prevalence in 3 to 4 year-olds (0.02 (95%CI 0.02 to 0.03)) and the highest prevalence in 15 to 17 year olds (1.38 (95%CI 1.36 to 1.40)). The administrative prevalence of ADHD is twice as high in CYP from the most deprived areas compared to CYP from the least deprived areas (1.14% (95%CI 1.12 to 1.16) in the most deprived areas to 0.64% (95%CI 0.63 to 0.65) in the least deprived areas)).\ud CYP with ADHD are at greater risk of fractures, thermal injuries and poisonings compared CYP without ADHD. In CYP with ADHD the incidence of fractures is 28% higher, thermal injuries is 104% higher and poisonings is 300% higher than in CYP without ADHD.\ud \ud Conclusions\ud \ud CYP with epilepsy and ADHD have an increased risk of fracture, thermal injury and poisoning compared to CYP without these conditions. For both conditions the risk of poisoning is higher than the risk of fractures or thermal injuries. The administrative prevalence of ADHD is lower than estimates of community prevalence ascertained from studies not using primary care data. The prevalence of ADHD varied with deprivation, being almost twice as high in CYP from the most deprived areas compared to CYP from the least deprived areas.\ud \ud \ud Future research is required to explore the circumstances surrounding injuries in CYP with and without epilepsy and ADHD. Future research is also required to explore the effect of treating epilepsy and ADHD with medication on injury risk. Research is required to explore the effect of the severity of epilepsy and ADHD on estimated risks of injuries. Future research exploring potential under-diagnosis or under-recording of diagnosis of ADHD in CYP in primary care is needed.\ud \ud CYP with epilepsy and ADHD and their parents should be provided with evidence-based injury prevention interventions because work in this thesis has demonstrated they are at higher risk of injury than the general population of CYP. Health care professionals working with CYP; child and adolescent mental health services; child education or care practitioners; and other agencies and organisations with an injury prevention role, should be made aware of the increased risk of injury in CYP with epilepsy and ADHD. Commissioners of health services for CYP should ensure service specifications include injury prevention training and provision for evidence-based injury prevention interventions