Incidence of hospital-acquired acute kidney injury and trajectories of glomerular filtration rate in older adults

Abstract

Background: In older adults, epidemiological data on incidence rates (IR) of hospital-acquired acute kidney injury (AKI) are scarce. Also, little is known about trajectories of kidney function before hospitalization with AKI.

Methods: We used data from biennial face-to-face study visits from the prospective Berlin Initiative Study (BIS) including community-dwelling participants aged 70+ with repeat estimated glomerular filtration rate (eGFR) based on serum creatinine and cystatin C. Primary outcome was first incident of hospital-acquired AKI assessed through linked insurance claims data. In a nested case-control study, kidney function decline prior to hospitalization with and without AKI was investigated using eGFR trajectories estimated with mixed-effects models adjusted for traditional cardiovascular comorbidities.

Results: Out of 2020 study participants (52.9% women; mean age 80.4 years) without prior AKI, 383 developed a first incident AKI, 1518 were hospitalized without AKI, and 119 were never hospitalized during a median follow-up of 8.8 years. IR per 1000 person years for hospital-acquired AKI was 26.8 (95% confidence interval (CI): 24.1-29.6); higher for men than women (33.9 (29.5-38.7) vs. 21.2 (18.1-24.6)). IR (CI) were lowest for persons aged 70-75 (13.1; 10.0-16.8) and highest for ≥ 90 years (54.6; 40.0-72.9). eGFR trajectories declined more steeply in men and women with AKI compared to men and women without AKI years before hospitalization. These differences in eGFR trajectories remained after adjustment for traditional comorbidities.

Conclusion: AKI is a frequent in-hospital complication in individuals aged 70 + showing a striking increase of IR with age. eGFR decline was steeper in elderly patients with AKI compared to elderly patients without AKI years prior to hospitalization emphasising the need for long-term kidney function monitoring pre-admission to improve risk stratification.

Keywords: AKI incidence; Acute kidney injury (AKI); Hospital-aquired AKI; In-hospital complication; Kidney function; Older adults; eGFR trajectories.

Fig. 1

Age and sex stratified incidence rate (per 1000 person years) of AKI in the study population

Fig. 2

Incidence rates (per 1000 person years) stratified by pre-existing comorbidities *Missing values: 6 values were missing for arterial hypertension, 12 values were missing for peripheral artery disease

Fig. 3

eGFR trajectories of individuals with AKI (green) and without AKI (red) for men and women calculated with a linear mixed-model in a nested case-control study eGFR trajectories were estimated with a mixed-effect model based on pooled results of multiple imputed data with 95% confidence intervals (grey area) for men with (n = 202) and without (n = 202) AKI and women with (n = 161) and without (n = 161) AKI .The x-axis shows the time (years) from inclusion into the study until hospitalization with or without AKI. To compare eGFR trajectories of individuals before hospitalization with AKI (cases) and without AKI (controls) we performed a nested case-control study with age at admission, sex, and length between study visit and hospitalization as matching criteria. The following variables were included in the model: age, log-transformed UACR (continuous), diabetes mellitus, arterial hypertension, congestive heart failure, peripheral artery disease, myocardial infarction, stroke, atrial fibrillation, BMI, smoking, polymedication (≥ 5 medication), number of prior hospitalizations, and log-transformed CRP (continuous) eGFR_BIS2: estimated glomerular filtration rate based on the creatinine and cystatin C-based BIS2 Eq. (15). BIS, Berlin Initiative Study. CI, confidence interval. AKI acute kidney injury. BMI, body mass index