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Scenario
A primary care practice followed 1,200 adults aged 65 and older for 12 months after their annual wellness visit. Polypharmacy was defined as taking five or more regular medications. The figures below are illustrative data created for this assignment.
| Fell within 12 months | Did not fall | Total | |
|---|---|---|---|
| Polypharmacy | 96 | 304 | 400 |
| No polypharmacy | 96 | 704 | 800 |
| Total | 192 | 1,008 | 1,200 |
Measures of frequency
- Cumulative incidence with polypharmacy: 96 / 400 = 24%.
- Cumulative incidence without polypharmacy: 96 / 800 = 12%.
- Overall incidence: 192 / 1,200 = 16%.
Measures of association
- Relative risk: 24% / 12% = 2.0. Older adults with polypharmacy were twice as likely to fall during the year.
- 95% confidence interval: the standard error of ln(RR) is √(1/96 − 1/400 + 1/96 − 1/800) = 0.131, so the interval is e^(ln 2 ± 1.96 × 0.131), or 1.55 to 2.58. It excludes 1, so the association is statistically significant at the .05 level.
- Attributable risk: 24% − 12% = 12 percentage points. Among people with polypharmacy, half of the falls, (24 − 12) / 24 = 50%, would be attributable to it if the association is causal.
- Population attributable fraction: (16% − 12%) / 16% = 25%. If the association were causal, removing the excess risk would prevent a quarter of the falls in this population (Celentano & Szklo, 2019).
Interpreting with caution
The association may be confounded. Older age, frailty, multiple chronic conditions and cognitive impairment are linked to both polypharmacy and falls, and the type of drug matters as well as the number: sedatives and other fall-risk-increasing drugs (FRIDs) carry more risk than, for example, a statin. Stratifying by age group or frailty and combining the strata with the Mantel–Haenszel method, or fitting a multivariable regression model, would estimate the association adjusted for these factors (Celentano & Szklo, 2019).
Population health implications
Even with these limits, the findings support routine medication review for older adults. The World Guidelines for Falls Prevention recommend medication review and appropriate deprescribing of FRIDs as part of multidomain falls prevention (Montero-Odasso et al., 2022). For this practice, a pharmacist-led review at each annual wellness visit for patients taking five or more medications is a practical next step.
References
Celentano, D. D., & Szklo, M. (2019). Gordis epidemiology (6th ed.). Elsevier.
Montero-Odasso, M., van der Velde, N., Martin, F. C., Petrovic, M., Tan, M. P., Ryg, J., Aguilar-Navarro, S., Alexander, N. B., Becker, C., Blain, H., Bourke, R., Cameron, I. D., Camicioli, R., Clemson, L., Close, J., Delbaere, K., Duan, L., Duque, G., Dyer, S. M., . . . Task Force on Global Guidelines for Falls in Older Adults. (2022). World guidelines for falls prevention and management for older adults: A global initiative. Age and Ageing, 51(9), Article afac205. https://doi.org/10.1093/ageing/afac205
