Healthcare use and costs associated with obesity in Badalona, Spain: a study protocol

INTRODUCTION: The objectives of the study are twofold. First, to calculate healthcare resource utilisation and costs for a cohort of adult overweight and obese patients observed in primary and hospital care centres during eight consecutive years (2003–2010) in an urban setting in Spain. An analysis of whether these costs vary by groups of individuals and types of disease, and of how they compare with the previous literature, is carried out in order to predict actions or policies for resource optimisation. The second objective is to estimate the impact of overweight and obesity on the consumption of resources and costs, accounting for a wide array of controls. METHODS AND ANALYSIS: Observational and retrospective cohort data are used, consisting of medical records of patients followed up in outpatient and hospital care facilities during the years 2003–2010. Three cohorts of patients are analysed: normal weight (18.5≥ body mass index (BMI) <25), overweight (25≥ BMI <30) and obese (BMI ≥30); BMI is computed using clinical information. Individual-level data on comorbidity, resource utilisation and costs are available, and external information provided by the population census regarding socioeconomic status is used. Utilisation and associated costs across BMI groups are compared by computing ratios for overweight and obese individuals relative to those of normal weight. Count data regression models (hurdle and finite mixture models) are used, together with two-part model regression models and taking into account the panel structure of the data set to explore the impact of overweight and obesity on the increased utilisation of health services and costs, accounting for a wide set of controls.