Longitudinal Estimated GFR Trajectories Among Workers at High Risk for CKD of Unknown Etiology

Chronic kidney disease (CKD) of unknown etiology is a leading cause of mortality among young men in Nicaragua and El Salvador, but longitudinal trends in kidney health and disease incidence remain poorly characterized.

We estimated glomerular filtration rate (eGFR) among young adult male workers in Nicaragua and El Salvador without known CKD (n = 569), aged 18 to 45 years, with follow-up every 6 months for 3 years. We estimated cumulative incidence of CKD, defined as ≥ 2 eGFR measurements < 60 ml/min per 1.73 m², and incidence rate in person-years. We used a hierarchical clustering approach to identify latent patterns in longitudinal eGFR.

Cumulative incidence was 4.5% (n = 24). Incidence rate was 22.2 cases per 1000 person-yrs (95% confidence interval [CI]: 13.6-30.9). All incident cases experienced eGFR decline > 5 ml/min per 1.73 m²/yr. Mean annual decline in eGFR was -4.3 ml/min per 1.73 m²/yr (SEM: 0.3). Cluster analyses revealed 4 eGFR trajectories described as declining, stable and high, rapidly declining, and low and declining. Participants in the low and declining cluster (n = 57; 10.9%) experienced mean annual eGFR decline of -8.2 ml/min per 1.73 m²/yr (SD: 0.7), with a pattern suggesting seasonal kidney stress and recovery. Participants in the rapidly declining cluster (n = 10) were very young men (mean age: 23 yrs) who experienced a precipitous decrease in eGFR (mean annual decline: -12.5 ml/min per 1.73 m²/yr (SD: 1.6)).

In this prospective cohort, we observed declining eGFR, including rapid decline in a young and apparently healthy subgroup. Relying on incidence measures alone may underestimate poor kidney health in the context of CKD of unknown etiology.