Polypharmacy and injurious falls in older adults: a nationwide nested case-control study

Abstract

Objective

To determine whether or not the exposure to multiple drugs (polypharmacy) increases the risk of fall-related injury among older adults, beyond the effect of fall-risk increasing drugs and chronic multimorbidity.

Methods

Nested case-control study using linked register data with national coverage in Sweden. We defined cases as older adults (≥70 years) who had an incident non-elective admission due to a fall between 1 January and 31 December 2013. Cases were matched 1:1 on sex, age and index date to randomly selected controls from the general population. The number of prescription drugs during the 7 days preceding the index date was the main exposure.

Results

A total of 49,609 cases were included and matched to an equal number of controls. The number of prescription drugs was higher among cases than among controls (mean difference 1.2, 95% CI 1.16–1.26). While adjusting for potential confounders, we found that the risk of injurious falls increased in a nearly linear fashion for each additional drug (OR, 1.02; 95% CI, 1.01–1.03). When using a cut-off value of ≥4 drugs to define polypharmacy, the population attributable fraction for injurious falls was 5.2% (95% CI 2.8–7.6).

Conclusion

This study shows a monotonic dose-response relationship between the number of drugs and the risk of injurious falls. However, after comprehensive adjustment for known confounders (including fall-risk increasing drugs and chronic multimorbidity), this association is substantially weaker than previously reported. Moreover, even if the relationship between polypharmacy and injurious falls is really causal, the population attributable risk fraction is low.

Keywords:

• polypharmacy
• falls
• case-control
• older people

Acknowledgments

The authors are grateful to Johan Fastbom for providing the software used to compute the exposure to polypharmacy. This work was supported by grants from the Swedish Research Council for Health, Working Life and Welfare and from the Swedish Research Council. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Availability of data and materials

Patient-level data from the Swedish Prescribed Drugs Register and other healthcare registers cannot be made publicly available. Interested researchers can access the aggregated data from the Swedish Prescribed Drugs Register (www.socialstyrelsen.se/statistik/statistikdatabas/lakemedel). Additional data can be obtained upon reasonable request to the authors.

Ethical statement

The study was approved by the Ethical Review Board in Stockholm, Sweden and was carried out in accordance with the principles of the Declaration of Helsinki.

Author contributions

LM conceived and designed the study, performed the statistical analysis, interpreted the data, drafted, and critically revised the manuscript. ACL, AKW, DR and JWW interpreted the data and critically revised the manuscript. KJ obtained funding, provided supervision, interpreted the data and, critically revised the manuscript. LM is the guarantors of the study and data integrity. All authors gave approval for the final version of the manuscript and agree to be accountable for all aspects of the work.

Disclosure

The authors declare that they have no conflicts of interest regarding this article.