Polypharmacy Linked to Higher Risk of Hospital Readmission

While polypharmacy, along with hospital length of stay and other factors, was linked to a higher risk of 30-day hospital readmission, the type of medication mattered as well.

Polypharmacy is a global problem among aging adults, and a recent study conducted in Switzerland examined the risk of 30-day hospital readmission of older adults taking many medications a day.

Specifically, the researchers sought to determine the impact of sociodemographic characteristics, medical and surgical diagnoses, clinical data such as gait, fall risk, or hearing issues, and drug regimen data with the risk of readmission among patients taking 5 or more daily prescriptions at the time the hospital sent them home.

Writing in BMJ Open, the authors noted that multimorbidity, polypharmacy, and inadequate drug management of prescriptions in older adults are significant risk factors for adverse drug events, which they said are the most common postdischarge complications, along with procedural complications and hospital-acquired infections.

Adverse drug events may result from “inappropriate drug prescribing, discrepancies between prescribed and current regimens, poor adherence, and the inadequate surveillance of adverse effects,” possibly leading to increased frailty and early death, they said.

This retrospective study analyzed the patient registry of a public hospital from 2015 to 2018. The electronic health records of 20,422 inpatient stays by older adults living at home included the 13,802 hospital readmissions of 8878 patients, an average of 1.55 inpatient hospital readmissions.

The mean [SD] age was 77.7 [7.48]; 57% were male. The average hospital length of stay was 8.44 days [7.58]. At the time they were sent home, 25% of the patients had impaired mobility, 4% were impaired in their activities of daily living, and 4% showed mental impairment. On average, 8.95 medications [3.24] were prescribed per patient at discharge.

The overall 30-day hospital readmission rate was 7.8%, in line with other published hospital readmission rates among community-dwelling older adults.

Results of an adjusted multivariate analyses showed that the following factors were associated with an increased risk of hospital readmission:

  • A longer length of stay: odds ratio (OR) = 1.014 per additional day; 95% CI, 1.006-1.021
  • Impaired mobility: OR = 1.218; 95% CI, 1.039-1.427
  • Multimorbidity: OR = 1.419 per additional disease; 95% CI, 1.282-1.572
  • Tumorous disease: OR = 2.538; 95% CI; 2.089-3.082

In addition, while polypharmacy carried an OR of 1.043 for each additional drug prescribed (95% CI, 1.028-1.058), certain drugs had higher risks than others:

  1. Antiemetics and antinauseants: OR = 3.216 per additional drug unit taken; 95% CI, 1.842-5.617
  2. Antihypertensives: OR = 1.771; 95% CI, 1.287-2.438
  3. Gastrointestinal medications: OR = 1.424; 95% CI, 1.166-1.739
  4. Systemic hormonal preparations: OR = 1.207; 95% CI, 1.052-1.385
  5. Vitamins: OR = 1.201; 95% CI, 1.049-1.374
  6. Concurrent use of beta-blocking agents and drugs for acid-related disorders: OR = 1.367; 95% CI, 1.046-1.788

At first, men with multiple illnesses were at a higher risk of readmission than women with multiple morbidities, the significance was not significant in an adjusted multivariate analysis. However, the authors noted that other studies have found that men were more likely to forget to take their medication or to implement a new dosage, leading to a high risk for readmission.

The study had several strengths, including 4-year data from a comprehensive hospital register; a range of characteristics to predict the probability of hospital readmission; and correlational analyses. However, clinically diagnosed drug–drug interactions were not included, and the researchers were unable to account for hospitalizations and readmissions lost to follow-up or to identify unnecessary hospitalizations, for instance.

The issue of what drives hospital readmissions “is an underinvestigated topic deserving of additional, well-conducted, predictive research exploiting accurate longitudinal data from large samples,” the authors concluded.


Pereira F, Verloo H, Zhivko T, et al. Risk of 30- day hospital readmission associated with medical conditions and drug regimens of polymedicated, older inpatients discharged home: a registry-based cohort study. BMJ Open. 2021;11:e052755. doi:10.1136/ bmjopen-2021-052755

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