The development of polypharmacy. A longitudinal study

BACKGROUND: To date, only a few studies have been carried out on the development and progress of polypharmacy in relation to morbidity in general practices in The Netherlands. OBJECTIVE: The aim of this study was to investigate the relationship between an increase in long-term drug use and the incidence and severity of some chronic diseases, particularly in the elderly. METHODS: Data on medication and morbidity of 1544 elderly people were collected for the period 1994-1997 from three family practices in the medication and morbidity Registration Network of Groningen (RNG) in the northern part of The Netherlands. Polypharmacy is defined as the long-term simultaneous use of two or more drugs; long-term is defined as >240 days in a year. We looked for differences in incidences of some chronic diseases in those subgroups of the elderly in whom multiple long-term drug use respectively increased, stayed constant or did not exist. Polypharmacy at the end of the period was predicted using regression analysis. RESULTS: Polypharmacy occurred in 42% of the elderly at the end of 1997, with major polypharmacy (>5 drugs) in only 4%. The average number of drugs used long-term increased from 1.3 to 1.8 in 4 years. Predictors for the increase of polypharmacy were the number of drugs at the start, age, diabetes, coronary ischaemic diseases and use of medication without a clear indication (P < 0.005). The average number of diseases also increased, especially in the elderly who showed the greatest increase in long-term drug use; however, there was no significant difference from the groups with a slow or no increase in drug use. DISCUSSION: Polypharmacy showed a slow increase over 4 years: almost 20% of the elderly developed polypharmacy, i.e. going from no drugs or one drug to two or more drugs. Polypharmacy develops mainly in elderly patients who already use several drugs, who are known to suffer from cardiovascular diseases, diabetes or stomach symptoms, those who often take drugs (especially sedatives/hypnotics) without clear indication and those who develop hypertension or atrial fibrillation over time.