Use of existing data sources in clinical epidemiology: Finnish health care registers in Alzheimer's disease research - the Medication use among persons with Alzheimer's disease (MEDALZ-2005) study.

Memory diseases are the most important determinant of health care service use and quality of life among older individuals. Adverse effects of medication are common among older people, but this age group is underrepresented in clinical trials. Finnish statutory health care and prescription registers, together with personal identification numbers (PINs) and a tax-supported public health plan covering all citizens provide excellent opportunities for epidemiological research. We used routinely collected data from the Finnish health care system to establish the Medication use among persons with Alzheimer's disease (MedAlz-2005) cohort. This cohort study will be used to assess medication use and its effects on health status and hospitalization among persons with Alzheimer's disease (Ad). The cohort includes all community-dwelling persons who had a clinically verified diagnosis of Ad, resided in Finland, and were alive on December 31, 2005 and a matched comparison person for each affected individual. data on purchased prescription medicines (1995-2009), inpatient hospital admissions (1972-2009), outpatient visits (1995-2009), details on diagnosed cancers (1972-2009), and mortality (until October 2010) are available for the whole cohort. This paper describes how this data can be utilized in etiological research and the assessment of health care service use, drug utilization, and associated adverse outcomes in a particularly vulnerable group that is often underrepresented in clinical trials.