Background: The simultaneous use of several medications is an important risk factor for injurious falls in older people. The aim of this study is to investigate the effect of the number of medications dispensed to elderly persons on fall injuries and to assess whether this relationship is explained by individual demographics, health habits and health status.
Methods: A population-based, nested, case-control study on people 65 years and older (N = 20.906) was conducted using data from the Stockholm Public Health Cohort (SPHC) derived from self-administered surveys and linked at the individual level with various Swedish health registers. Fall injuries leading to hospitalization recorded in the Swedish National Patient Register (NPR) were considered as the outcome. The main exposure, obtained from the Swedish Prescribed Drug Register (SPDR), was the number of medications dispensed within 90 days prior to the injurious fall. The injury risk was estimated using adjusted odds ratios (ORs) from logistic regression. Results were adjusted by selected demographic, social circumstances, lifestyle and health status data extracted from the SPHC.
Results: After adjusting for common risk factors within demographics, lifestyle, social circumstances and health status, using more than one medication increased the risk of fall injury but no clear dose-response relationship was observed, with point estimates ranging from 1.5-1.7 for the use of two, three, four or five or more medications as compared to using none. An increased risk remained, and was even elevated, after adjusting for the use of fall-risk-increasing drugs (FRIDs).
Conclusions: Using more than one medication affects the risk of injurious falls among older people. The effect of any given number of medications studied remains and is even strengthened after adjusting for individual demographics, health habits, health conditions and the use of FRIDs.