Introduction: Polypharmacy, the use of multiple medications by one individual, is increasingly common among older adults. Caring for the growing number of older people with complex drug regimens and multimorbidity presents an important challenge in the coming years.Areas covered: This article reviews the international trends in the prevalence of polypharmacy, summarizes the results from previous reviews on polypharmacy and negative health outcomes, and updates a previous review on the clinical consequences of polypharmacy by focusing on studies published after 2013. This narrative review, which is based on a literature search in MEDLINE and EMBASE from January 1990 to June 2018, was undertaken to identify relevant articles. Search terms included variations of polypharmacy and multiple medications. Expert opinion: The prevalence of polypharmacy is increasing worldwide. More than half of the older population is exposed to polypharmacy in some settings. Polypharmacy is associated with a broad range of clinical consequences. However, methods to assess the dangers of polypharmacy should be refined. In our opinion, the issue of 'confounding by multimorbidity' has been underestimated and should be better accounted for in future studies. Moreover, researchers should develop more clinically relevant definitions of polypharmacy, including measures of inappropriate or problematic polypharmacy.

ObjectivePolypharmacy is the concomitant use of several drugs by a single person, and it increases the risk of adverse drug-related events in older adults. Little is known about the epidemiology of polypharmacy at the population level. We aimed to measure the prevalence and incidence of polypharmacy and to investigate the associated factors.MethodsA prospective cohort study was conducted using register data with national coverage in Sweden. A total of 1,742,336 individuals aged ≥65 years at baseline (November 1, 2010) were included and followed until death or the end of the study (December 20, 2013).ResultsOn average, individuals were exposed to 4.6 (SD =4.0) drugs at baseline. The prevalence of polypharmacy (5+ drugs) was 44.0%, and the prevalence of excessive polypharmacy (10+ drugs) was 11.7%. The incidence rate of polypharmacy among individuals without polypharmacy at baseline was 19.9 per 100 person-years, ranging from 16.8% in individuals aged 65–74 years to 33.2% in those aged ≥95 years (adjusted hazard ratio [HR] =1.49, 95% confidence interval [CI] 1.42–1.56). The incidence rate of excessive polypharmacy was 8.0 per 100 person-years. Older adults using multi-dose dispensing were at significantly higher risk of developing incident polypharmacy compared with those receiving ordinary prescriptions (HR =1.51, 95% CI 1.47–1.55). When adjusting for confounders, living in nursing home was found to be associated with lower risks of incident polypharmacy and incident excessive polypharmacy (HR =0.79 and HR =0.86, p<0.001, respectively).ConclusionThe prevalence and incidence of polypharmacy are high among older adults in Sweden. Interventions aimed at reducing the prevalence of polypharmacy should also target potential incident polypharmacy users as they are the ones who fuel future polypharmacy.

This systematic review shows that almost one-half of nursing home residents are exposed to potentially inappropriate medications and suggests an increase prevalence over time. Effective interventions to optimize drug prescribing in nursing home facilities are, therefore, needed.