The global population is ageing rapidly, leading to a rising prevalence of chronic conditions among older adults. Multimorbidity, defined as the coexistence of two or more chronic diseases, is particularly common in the elderly and poses significant challenges for clinical management (1). In response to complex health needs, polypharmacy—the use of multiple medications—has become increasingly prevalent. While polypharmacy is often necessary to manage multimorbidity, it can lead to adverse drug reactions, drug–drug interactions, medication non-adherence, and poor therapeutic outcomes (2,3).

Hospital readmissions within 30 days of discharge are considered a key indicator of healthcare quality and efficiency. Among elderly patients with multiple comorbidities, readmission rates are particularly high and frequently preventable (4). Several studies have suggested a strong correlation between polypharmacy and increased risk of hospital readmission, primarily due to medication-related complications (5,6). Furthermore, the burden of polypharmacy complicates discharge planning and continuity of care, especially in patients with cognitive decline or limited social support (7).

Despite the widespread recognition of this issue, the extent to which polypharmacy independently contributes to readmission risk remains underexplored in certain healthcare settings, particularly in low- and middle-income countries. Evaluating this association is essential for developing strategies aimed at deprescribing and improving transitional care in geriatric populations (8).

This study aims to assess the impact of polypharmacy on 30-day hospital readmission rates among elderly patients with multimorbidity, providing insight into an important, yet modifiable, risk factor for adverse outcomes.

This retrospective observational study was conducted at a tertiary care hospital over a 12-month period. The study population included patients aged 65 years and above who were admitted for medical conditions and discharged to home after treatment. Eligibility criteria required each patient to have at least two documented chronic diseases (e.g., hypertension, diabetes, chronic kidney disease, COPD). Patients discharged to nursing homes, those who died during hospitalization, or had incomplete medical records were excluded from the analysis.

Data were collected from electronic health records, including demographic details (age, gender), clinical information (number and type of chronic conditions), medication lists at discharge, length of hospital stay, and 30-day readmission status. Polypharmacy was classified into three categories:

• Non-polypharmacy: fewer than 5 prescribed medications
• Moderate polypharmacy: 5 to 9 medications
• Excessive polypharmacy: 10 or more medications

The primary outcome measure was hospital readmission within 30 days of discharge, defined as an unplanned return to the hospital for any cause. Secondary data, such as comorbidity burden (using Charlson Comorbidity Index), and functional status (assessed through documented clinical notes), were also analyzed to adjust for confounding variables.

Statistical analysis was performed using SPSS version 26.0. Descriptive statistics were used to summarize patient characteristics. Chi-square tests were employed to examine associations between polypharmacy categories and readmission rates. A multivariable logistic regression model was used to determine the independent effect of polypharmacy on readmission, adjusting for age, gender, comorbidity index, and functional status. A p-value of <0.05 was considered statistically significant

A total of 300 elderly patients met the inclusion criteria for this study. The mean age of the participants was 73.6 ± 6.4 years, with a slight female predominance (52%). The most common chronic conditions were hypertension (72%), type 2 diabetes mellitus (65%), and osteoarthritis (48%).

Polypharmacy Distribution and Readmission Rates

Patients were categorized based on the number of medications prescribed at discharge: 60 (20%) had non-polypharmacy (<5 medications), 150 (50%) had moderate polypharmacy (5–9 medications), and 90 (30%) had excessive polypharmacy (≥10 medications). The 30-day hospital readmission rate increased with the level of polypharmacy, being 10% in the non-polypharmacy group, 22% in the moderate polypharmacy group, and 38% in the excessive polypharmacy group (Table 1).

Table 1: Distribution of Patients and 30-Day Readmission Rates by Polypharmacy Level

The association between polypharmacy and readmission was statistically significant (p<0.01, chi-square test), indicating a direct relationship between increasing medication load and risk of rehospitalization (Table 1).

Logistic Regression Analysis

Multivariable logistic regression analysis was conducted to identify independent predictors of 30-day readmission. After adjusting for age, gender, Charlson Comorbidity Index, and functional status, excessive polypharmacy remained a significant predictor (Odds Ratio: 3.5; 95% CI: 1.8–6.9; p<0.001), while moderate polypharmacy showed a moderate but significant association (Odds Ratio: 2.1; 95% CI: 1.1–3.9; p=0.02) (Table 2).

Table 2: Logistic Regression Analysis of Factors Associated with 30-Day Readmission

As shown in Table 2, higher comorbidity scores and polypharmacy levels were independently associated with increased odds of hospital readmission, supporting the hypothesis that medication burden significantly affects post-discharge outcomes.

This study demonstrated a clear and statistically significant association between polypharmacy and 30-day hospital readmission rates among elderly patients with multimorbidity. Specifically, individuals prescribed ten or more medications at discharge were over three times more likely to be readmitted compared to those on fewer than five medications, even after adjusting for potential confounding variables such as age, comorbidity burden, and functional status.

Polypharmacy has long been recognized as a major contributor to adverse clinical outcomes in older adults. The increasing complexity of pharmacotherapy in the context of multiple chronic diseases often leads to drug–drug interactions, prescribing cascades, and poor medication adherence—all of which are implicated in hospital readmissions (1,2). Our findings are consistent with prior studies that identified polypharmacy as a strong independent predictor of rehospitalization (3,4).

The elderly are especially vulnerable to the consequences of polypharmacy due to age-related pharmacokinetic and pharmacodynamic changes, as well as the frequent presence of cognitive impairment and functional decline (5). Excessive medication use has been linked not only to adverse drug events but also to medication errors during transitions of care—a critical period when medication reconciliation is often suboptimal (6,7).

In the present study, a significant portion of the cohort (80%) was prescribed five or more medications, reflecting the high prevalence of polypharmacy in geriatric populations globally (8). This aligns with other reports indicating that over half of older adults with multiple comorbidities are exposed to polypharmacy, often without regular review of drug necessity or appropriateness (9,10).

Our results further emphasize the need for targeted interventions, such as comprehensive medication reviews, deprescribing protocols, and pharmacist-led discharge planning, which have been shown to reduce the number of inappropriate prescriptions and subsequent readmission rates (11,12). The role of clinical decision support systems and multidisciplinary care teams is also critical in minimizing the risks associated with polypharmacy (13).

Another factor influencing readmissions in this study was the comorbidity burden, which is consistent with earlier research showing that higher Charlson Comorbidity Index scores are predictive of poor post-discharge outcomes (14, 15). However, even after controlling for comorbidity, polypharmacy remained an independent and modifiable risk factor.

In conclusion, excessive polypharmacy is strongly associated with increased 30-day hospital readmission rates in elderly patients with multimorbidity. Interventions aimed at optimizing pharmacotherapy during hospitalization and at discharge should be prioritized to enhance the safety and quality of care for this vulnerable population

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