Using Propensity Score Matching Technique to Estimate Utilization and Costs of General Practitioners’ Services associated with Alzheimer’s Disease

Abstract

Objective: General practitioners (GPs) play an important role in caring for people with Alzheimer's disease (AD). However, the cost and the extent of service utilization from GPs due to AD patients are difficult to assess. This study aimed to explore the principles of propensity score matching (PSM) technique to assess the additional GP service use and cost imposed by AD in persons aged ≥60 years in Denmark.Design: PSM was used to estimate the additional use and cost of GP services attributable to AD. Case and control baseline characteristics were compared with and without the application of PSM. Propensity scores were then estimated using the generalized boosted model, a multivariate, nonparametric and automated algorithm technique.Setting: Observational data from Statistics Denmark registry.Subjects: 3368 cases and 3368 controls; cases with AD were defined as patients with diagnoses G30 and F00 and/or those with primary care prescriptions for anti-AD drugs from the years 2004 until 2009. Main Outcome Measures: GP service utilisation and costs attributable to AD.Results: PSM brought a large improvement to the balance of observed covariates among the cases and control groups. AD patients received around 20% more GP services and utilized services that cost 15% more than non-AD controls during a calendar year.Conclusion: AD patients utilize more GP services and incur higher costs as compared to their matched controls. The PSM technique can be an effective tool to reduce imbalance of observable confounders from register based data and improve the estimations. JHEORSharma R, et al. 68JHEOR 2016;4(1):67-79 | www.jheor.org BACKGROUND Alzheimer's disease (AD) is a clinical syndrome caused by non-reversible neurodegeneration and is characterized by severe deterioration in cognitive ability. 1 The World Health Organization (WHO) has projected that AD and dementia will become the third-leading cause of burden of disease by 2030. 2 Around 15 000 new dementia cases are detected every year in Denmark. 3 The majority of dementia cases are AD patients. The prevalence of AD is projected to rise in the future with more elderly people and longer life expectancy. In Denmark, General Practitioners (GPs) are the primary caregivers for most chronic conditions. They play an important role in diagnostic evaluation and ongoing care as well as provide usual consultation services. 4 It is important to ascertain the difference in GP services use and cost between those with and without AD to assist with planning for future disease management. When the attributable cost related to dementia is estimated, it is important that the comparison is made for people with similar characteristics. That can be achieved by some form of matching technique. Propensity Score Matching (PSM) appears to offer a better match of observational covariates than simple sub-group matching. In comparison to other traditional regression methods, PSM has two major strengths. First, the matched cases and controls are only selected if they lie within the pre-assigned 'comm...