Correlates of polypharmacy and prescription changes in internal medicine: a prospective five-year study.

Background: Data regarding polypharmacy in the internal medicine setting remain limited. We aimed to assess the prevalence of polypharmacy, examine its associations with clinical and socioeconomic factors, and evaluate its impact on mortality.

Methods: This was part of the San MAtteo Complexity (SMAC) study (2017-2025), conducted in an internal medicine service of an academic medical center. Patients were consecutively and prospectively enrolled. Polypharmacy prevalence was assessed at admission and discharge. Sociodemographic data, Cumulative Illness Rating Scale (CIRS), Edmonton Frail Scale, comorbidity, multimorbidity, Short Blessed Test, and Barthel Index were collected. Associations with polypharmacy were analyzed using logistic regression, and early and late mortality were tracked using Kaplan-Meier analysis.

Results: Among 1419 patients (median age 80 years, IQR 69-86; F:M ratio 1.14:1), polypharmacy was observed in 71.5% at admission and 82.6% at discharge. Patients with polypharmacy were significantly older, frailer, and had lower socioeconomic status. Independent predictors included age ≥65 years (OR 4.14, 95% CI 1.60-10.69), CIRS >3 (OR 2.67, 95% CI 1.98-3.58), frailty (OR 3.85, 95% CI 0.68-1.50), comorbidity (OR 8.2, 95% CI 2.19-30.7), multimorbidity (OR 20.91, 95% CI 5.65-77.44), and cardiovascular disorders (OR 1.84, 95% CI 1.33-2.55). In-hospital and 4-month mortality were significantly higher among patients who were deprescribed (i.e., discharged with ≤5 fewer medications). Five-year mortality was significantly higher in patients with polypharmacy (HR 2.83, 95% CI 2.07-3.86; p<0.001), regardless of prescription changes.

Conclusions: Polypharmacy is highly prevalent in internal medicine, and both deprescribing and polypharmacy are associated with increased mortality at different timepoints, underscoring the need for targeted medication optimization strategies.