Economic implications of intellectual disability in childhood : a trial-based evaluation

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Childhood intellectual disability (ID) has a significant impact on individuals, families, society and the healthcare system. This thesis explores the economic implications of an early behavioural intervention designed to lessen these impacts, Stepping Stones Triple P (SSTP). Innovative methods are used to contribute the body of knowledge that can guide economic evaluations in this population. Particular attention is given to the inclusion of caregiver effects in economic evaluations. SSTP is a parenting program that is designed for families of children that have a disability. It adopts a public health approach and aims to prevent and treat behavioural and emotional problems in children. It is a multilevel program with varying levels of intensity available depending on the needs of the child and the family. Data collected alongside a trial evaluating the public health roll-out of SSTP were utilised throughout this thesis. An overview of SSTP and the trial evaluating SSTP are described in Chapter 2. This thesis comprises five related studies. The first study, presented in Chapter 3, describes the health-related quality of life (HRQoL) of caregivers who care for a child with ID. This study demonstrated that caregivers have a lower HRQoL than the age-equivalent general population. This study provides utility values of caregivers of children with ID across five comorbid disability groups (autism spectrum disorders, genetic disabilities, physical disabilities, sensory disabilities and language disabilities) that can be used to inform comparative cost-effectiveness analyses. In Chapter 4 a discrete choice experiment was developed to estimate a monetary value of informal care tasks provided by caregivers of children with ID. The values generated by this methodology were lower than would be expected using traditional approaches, and may reflect the satisfaction and pleasure derived by an individual from providing care for a family member. The values generated in this study can be used directly in economic evaluations to estimate the cost of informal care. Chapter 5 compares the use of a time-use diary and recall questionnaire to measure the time spent providing informal care. The results demonstrated the considerable caregiver burden of childhood ID, with an average of five to six hours of care provided due to the child’s disability per day. Analysis of the two methodologies showed that the recall questionnaire overestimated the time spent providing informal care, which may be a result of recall bias, an inability to adjust for joint production or double counting of normal caregiver tasks. This chapter highlighted that the methods chosen to measure informal care can have important implications when considering the relative costs and benefits of competing interventions. Chapter 6 presents analyses which measure the costs associated with caring for a child with ID. Trial-based data and linked administrative data were used to measure medical service use and pharmaceutical use in children and caregivers, and the productivity of caregivers. Estimates from Chapters 5 and 6 were used to calculate the total societal cost of childhood ID. The total cost to society of childhood ID was estimated to be between $9.126 billion and $14.159 billion per year. The cost of time spent caregiving accounts for the largest proportion of the total cost. The final component of this research, presents the results of a cost-consequence analysis of SSTP (Chapter 7). The costs associated with implementing SSTP are compared to benefits derived from SSTP and other cost savings estimated in the preceding chapters. The cost of SSTP ranged from $2,661-$10,800 per family depending on the level of intervention delivered and method of implementation. Cost savings realised included productivity gains due to a lower frequency of caregiver absenteeism and reduced costs of informal care doing household errands. SSTP also resulted in an increase in costs to government, families and society due to increased service use by caregivers. Other benefits were also realised, including a reduction in child behavioural and emotional problems, improvements in parenting practices, improvements in family practices and reduced caregiver stress. The findings show that SSTP can represent excellent value for money, improving outcomes at low cost. This thesis demonstrates the considerable burden associated with ID and the need for evidence-based interventions that can improve outcomes for this group. It demonstrates the significant role provided by caregivers and provides innovative methods for measuring and valuing informal care that can be applied to economic evaluations of complex interventions.
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