(063) Association between Polypharmacy and the Risk of Chronic Kidney Disease in the Elderly Patients

Background: Polypharmacy, the utilization of multiple drugs beyond medical necessity, is increasingly concerning for the elderly population. Polypharmacy might pose a significant risk to the kidneys, as it imposes a heavy burden in eliminating numerous drugs and their metabolites, thus potentially increasing the risk of chronic kidney disease (CKD).

Objectives: To investigate whether polypharmacy is associated with an increased risk of CKD in the elderly.

Methods: We conducted a retrospective cohort study using the National Sample Cohort database (NSC DB), which includes medical information from one million individuals sampled, obtained from Korea's National Health Insurance Service (NHIS) for the period between 2013 to 2019. The study population included those aged over 65 as of 2014. Patients diagnosed with CKD within 2 years prior to the index date (January 1, 2015) or those who had an average number of prescriptions per day in 2013 of five or more were excluded from the study. Polypharmacy was defined as the concomitant use of five or more drugs per day, while non-polypharmacy was defined as the concomitant use of less than five drugs. To calculate the average number of prescriptions per day, the total prescription days for each drug substance code prescribed throughout 2014 were summed and then divided by 365. The cases of CKD (ICD-10 code: N18 and N19) was confirmed by primary or secondary diagnosis records in outpatient or inpatient settings. Patients were followed from the date of the index date until the earliest diagnosis of CKD, death, or the end of the study period. We performed 1:4 propensity score matching and estimated incidence rate ratio (IRR) with a 95% confidence interval (CI) using conditional Poisson regression model, adjusted for sex, age, residence, Charlson comorbidity index (categorized as 0, 1, and ≥2), and disease risk factors for CKD (hypertension, diabetes mellitus, congestive heart failure, ischemic heart disease, hyperlipidemia, arrhythmia, and gout), in the year before the index date. Additionally, we calculated the incidence rates per 1,000 person-years and conducted subgroup analysis by gender.

Results: Of the 86,220 patients included in the cohort, 41,256 (polypharmacy: 8,266; non-polypharmacy: 32,990) were retained after propensity score matching. In the matched cohort, the polypharmacy group showed a higher risk of CKD (adjusted IRR: 1.89, 95% CI: 1.68-2.14). In the polypharmacy group, CKD incidence was 9.44 per 1,000 person-years, compared to 4.98 in the non-polypharmacy group. The results of the subgroup analysis by gender were consistent with the main analysis.

Conclusions: Our findings showed that polypharmacy might be associated with a high risk of CKD in elderly. Further study is needed to confirm polypharmacy risk based on drug types.