Polypharmacy Thresholds that Best Predict Emergency Room Visits and Mortality in Older Adults: A Population-Based Study in Québec, Canada

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Abstract
Background: Polypharmacy is prevalent among older adults. Identifying informative medication thresholds could enhance clinical decision-making and healthcare planning. Objectives: To measure the predictive capacity of medication count and polypharmacy thresholds on (1) frequent emergency visits and (2) mortality, in community-dwelling older adults in Quebec, Canada; To measure the predictive capacity of inappropriateness criteria (potentially inappropriate medications, anticholinergic burden level, and drug–drug interactions) on these same outcomes. Methods: We conducted a population-based study using the Quebec Integrated Chronic Disease Surveillance System. Using multivariable logistic regression models, we assessed the predictive capacity [area under the curve (AUC)] of medication use (medication count, polypharmacy thresholds, number of inappropriateness criteria) on frequent emergency visits (≥3) and mortality from April 2, 2022, to March 31, 2023. Findings were interpreted from two perspectives: clinical (with models including individuals’ clinical characteristics, such as chronic diseases) and public health (with models excluding clinical characteristics to mimic polypharmacy measures usually used in surveillance). Results: Medication count remained the most informative predictor in the clinical perspective analyses, with AUC = 0.739 for frequent emergency visits and AUC = 0.804 for one-year mortality, while medication thresholds lacked discrimination. Public health perspective analyses resulted in a bell-shaped predictive pattern peaking at eight medications for both frequent emergency visits (AUC = 0.690) and one-year mortality (AUC = 0.764). Inappropriateness criteria did not outperform medication count or polypharmacy thresholds. Conclusion: From a clinical perspective, medication count is more informative than polypharmacy thresholds. From a public health perspective, a threshold of eight medications may serve as a useful polypharmacy measure.
Funding Information
  • Canadian Institute of Health Research and the Natural Sciences and Engineering Research Council of Canada (CPG—170621)
  • Santé (Junior 2 salary grant)

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