Polypharmacy and Kidney Function in Community-Dwelling Adults Age 60 Years and Older: A Prospective Observational Study

Objectives: Information on the impact of polypharmacy on kidney function in older adults is limited. We prospectively investigated the association between intake of total number of drugs or nonsteroidal anti-inflammatory drugs (NSAIDs) and kidney function.

Design: Our study is a prospective observational analysis of the 2-year Zurich Multiple Endpoint Vitamin D Trial in Knee Osteoarthritis Patients.

Setting and participants: Of the 273 participants of the original trial, 270 participants (mean age 70.3 ± 6.4 years, 53% women) were included in this observational analysis.

Methods: The associations between (1) total number of drugs (or NSAIDs) at baseline or (2) cumulative number of drugs (or NASAIDs) repeatedly measured over 24 months and kidney function repeatedly measured over 24 months as estimated glomerular filtration rate (eGFR) were investigated using multivariable-adjusted repeated-measures analysis.

Results: Per drug at baseline, kidney function decreased by 0.64 mL/min/1.73 m² eGFR (Beta = -0.64; 95% CI -1.19 to -0.08; P = .024) over 24 months. With every additional drug taken cumulatively over 24 months, kidney function decreased by 0.39 mL/min/1.73 m² eGFR (Beta = -0.39; 95% CI -0.63 to -0.15; P = .002). In a high-risk subgroup, per NSAID taken cumulatively over 24 months, kidney function declined by 1.21 mL/min/1.73 m² eGFR (Beta = -1.21; 95% CI -2.35 to -0.07; P = .021).

Conclusions and implications: For every additional drug prescribed among older adults, our study supports an independent and immediate harmful impact on kidney function. This negative impact seems to be about 3 times greater for NSAIDs compared with an additional average drug.