Objectives: To investigate the association between polypharmacy and medication regimen complexity with time to first hospitalization, number of hospitalizations, and number of hospital days over a 12-month period.

Design: A 12-month prospective cohort study.

Participants and Setting: A total of 383 residents of 6 Australian long-term care facilities (LTCFs).

Measurements: The primary exposures were polypharmacy (≥9 regular medications) and the 65-item Medication Regimen Complexity Index (MRCI). Cox proportional hazards regression was used to compute hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between polypharmacy and MRCI with time to first hospitalization. Poisson regression was used to compute incident rate ratios (IRR) and 95% CIs for the association between polypharmacy and MRCI with number of hospitalizations and number of hospital days. Models were adjusted for age, sex, length of stay in LTCF, comorbidities, activities of daily living, and dementia severity.

Results: There were 0.56 (95% CI 0.49-0.65) hospitalizations per person-year and 4.52 (95% CI 4.31-4.76) hospital days per person-year. In adjusted analyses, polypharmacy was associated with time to first hospitalization (HR 1.84; 95% CI 1.21-2.79), number of hospitalizations (IRR 1.51; 95% CI 1.09-2.10), and hospital days per person-year (IRR 1.39; 95% CI 1.24-1.56). Similarly, in adjusted analyses a 10-unit increase in MRCI was associated with time to first hospitalization (HR 1.17; 95% CI 1.06-1.29), number of hospitalizations (IRR 1.15; 95% CI 1.06-1.24), and hospital days per person-year (IRR 1.19; 95% CI 1.16-1.23).

Conclusions: Polypharmacy and medication regimen complexity are associated with hospitalizations from LTCFs. This highlights the importance of regular medication review for residents of LTCFs and the need for further research into the risk-to-benefit ratio of prescribing in this setting.