Epidemiology and Associated Factors of Polypharmacy in Older Patients in Primary Care: a Northern Italian Cross-sectional Study

Background: A precondition for developing strategies to reduce polypharmacy and its well-known harmful consequences is to study its epidemiology and associated factors. The objective of this study was to analyse the prevalence of polypharmacy (defined as ≥8 prescribed drugs), of potentially inappropriate medications (PIMs) and major drug-drug interactions (DDIs) among community-dwelling general practice patients aged ≥75 years and to identify characteristics being associated with polypharmacy.

Methods: This cross-sectional study is derived from baseline data (patients' demographic/biometric characteristics, diagnoses, medication-related data, cognitive/affective status, quality of life) of a northern-Italian cluster-RCT. PIMs and DDIs were assessed using the 2012 Beers criteria and the Lexi-Interact® database. Data were analysed using descriptive methods, Wilcoxon rank-sum tests, Fisher's exact tests and Spearman correlations.

Results: Of the eligible patients aged 75+, 13.4% were on therapy with ≥8 drugs. Forty-three general practitioners and 579 patients participated in the study. Forty five point nine percent of patients were treated with ≥1 Beers-listed drugs. The most frequent PIMs were benzodiazepines/hypnotics (19.7% of patients) and NSAIDs (6.6%). Sixty seven point five percent of patients were exposed to ≥1 major DDI, 35.2% to ≥2 major DDIs. Antithrombotic/anticoagulant medications (30.4%) and antidepressants/antipsychotics (23.1%) were the most frequently interacting drugs. Polypharmacy was significantly associated with a higher number of major DDIs (Spearman's rho 0.33, p < 0.001) and chronic conditions (Spearman's rho 0.20, p < 0.001), higher 5-GDS scores (thus, lower affective status) (Spearman's rho 0.12, p = 0.003) and lower EQ-5D-5L scores (thus, lower quality of life) (Spearman's rho - 0.14, p = 0.001). Patients' age/sex, 6-CIT scores (cognitive status), BMI or PIM use were not correlated with the number of drugs.

Conclusions: The prevalence of polypharmacy, PIMs and major DDIs was considerable. Results indicate that physicians should particularly observe their patients with multiple conditions, reduced health and affective status, independently from other patients' characteristics. Careful attention about indication, benefit and potential risk should be paid especially to patients on therapy with specific drug classes identified as potentially inappropriate or prone to major DDIs in older persons (e.g., benzodiazepines, NSAIDs, protonic pump inhibitors, antithrombotics/anticoagulants, antidepressants/antipsychotics).

Trial Registration: The cluster-RCT on which this cross-sectional analysis is based was registered with Current Controlled Trials Ltd. (ID ISRCTN: 38449870 ) on 2013-09-11.