Prevalence of polypharmacy: a cross-sectional study in Singapore public healthcare institutions.

INTRODUCTION: Polypharmacy is associated with increased prevalence of potentially inappropriate medications (PIMs), leading to higher risk of adverse drug events and medication errors. This study was the first multicentre cross-sectional study in Singapore that determined the prevalence of polypharmacy, its associated factors and the common drug classes involved, and evaluated prescribing appropriateness of drugs used by older adults. METHODS: The prescriptions on two randomly selected days from five acute care hospitals and primary care polyclinics were retrospectively reviewed. Patients' demographic characteristics, number of prescription line items and details of prescribed drugs were collected. Prescribing appropriateness was evaluated by identifying PIMs using the Beers Criteria. Logistic regression was used to assess the association of demographic characteristics and type of care setting with polypharmacy and PIM use. RESULTS: Prevalence of polypharmacy was significantly higher in hospitals than in polyclinics (66.6% vs. 35.0%, P < 0.001). On the contrary, prevalence of PIMs in older adults with polypharmacy was significantly higher in polyclinics than in hospitals (34.6% vs. 27.1%, P = 0.010). Patients aged ≥65 years and hospitalised patients had higher odds of having polypharmacy than patients aged 21-64 years and polyclinic patients, respectively. Drugs used for chronic conditions commonly contributed to polypharmacy in both care settings. The top PIMs in hospitals and polyclinics were drugs for functional gastrointestinal disorders and systemic antihistamines, respectively. CONCLUSION: With the ageing population and growing burden of chronic disease in Singapore, increase in prevalence of polypharmacy is expected. More focus should thus be placed on reducing inappropriate polypharmacy.