4.3. Data collection and the Anatomical Therapeutic Chemical (ATC) classification system

The personal interviews were made by two trained nurses in Härkätie Health Center, Lieto. The subjects had been asked to take their presciptions and drugs along to show the medication that they were currently taking. The nurses also confirmed the respondents’ medication use with a close relative or a care-giver or from home nursing and the medical records of the health center, if the person was unable to answer questions, had dementia, or was not in a good condition. If the subject was unable to visit the health center, a trained nurse made a home visit to check the medications in use. Two health center physicians who belonged to the research team also reviewed the information on medications and collected the participants’ diagnoses from the medical records.

The brand names of all prescription drugs (both regular and irregular medication) taken by the interviewee during seven days prior to the interview were recorded and categorized during both study periods by the ATC classification system of National Agency for Medicines (2000): Classification of Medicines (ATC) and Defined Daily Doses (DDD) 2000. Because the ATC codes of some drugs had changed between 1990–91 and 1998–99, they were re-coded according to the classification of the year 2000 to attain comparable recording. The ATC system was created by the Nordic Council on Medicines, version 1996 (Nordic Council on Medicines 1996, National Agency for Medicines 2000), and has been recommended by WHO (1995). In the ATC system, the drugs are divided into different groups according to the organ or system on which they act and their chemical, therapeutic, and pharmacological properties (National Agency for Medicines and Social Insurance Institution 2001). The drugs are classified into 14 main groups at 5 different levels. For example, furosemide is coded as C03CA01 (C = cardiovascular, C03 = diuretics, C03C = high-ceiling diuretics, C03CA = sulphonamides, C03CA01 = chemical substance furosemide) and diazepam as N05BA01 (N = nervous system, N05 = psycholeptics, N05B = anxiolytics, N05BA = benzodiazepines, N05BA01 = chemical substance diazepam).