Prevalence of chronic disease in the elderly based on a national pharmacy claims database

SIR—The elderly are the fastest growing sector of society with those ≥70 years of age accounting for nearly 8% of the Irish population [1, 2]. Yet there is little or no baseline information on the prevalence of chronic disease in this population [3]. This lack of information on health trends can inhibit accurate predictions for future health care needs in this age group. The most recent data on prevalence of chronic disease were reported in the 2000 ‘Health and Social Services for Older People I’ (HeSSOP I) survey [4], which relied on selfreported illness and involved 937 community-dwelling adults ≥65 years of age. HeSSOP I provides insight into the prevalence of certain chronic conditions. However, this was not the primary purpose of the survey, and disease definition was vague, for example, ‘memory/concentration problems’. It is also likely to underestimate disease prevalence as it excludes those in nursing homes. This article explores the potential for using a national pharmacy claims database to estimate prevalence of disease. The data are readily available, are collected on a continuous basis and cover the majority of prescribing in those aged ≥70 years. However, the data are not diagnosis linked; thus, combination of drug therapies are used as surrogate markers of disease [5]. This approach lacks specificity for certain conditions as some drugs have broad licensed indications; however, this method has been used and validated in other settings [6–11]. The aim of this study was to estimate chronic disease prevalence in an elderly national population using an existing prescribing claims database.