Baseline and 4-year associations between prediabetes and kidney impairment: Insights from the ILERVAS cohort

Prediabetes is a prevalent condition associated with increased cardiovascular and renal risk. However, the long-term impact of haemoglobin A1c (HbA1c) within the range defined as prediabetes on kidney function remains unclear. This study aimed to evaluate the association between prediabetes and renal function (estimated glomerular filtration rate [eGFR] and albuminuria) through cross-sectional and prospective analyses over 4 years in a cohort of individuals with no diagnosis of diabetes or established cardiovascular disease.

Analysis using data from 8153 participants in the ILERVAS cohort, a prospective cross-sectional study. Prediabetes was defined as HbA1c 5.7%-6.4% (ADA criteria). Kidney impairment was defined as eGFR <60 mL/min/1.73 m² and/or urinary albumin-to-creatinine ratio (ACR) ≥30 mg/g at a single time point. A prospective study was conducted in 3222 participants, who were reassessed after 4 years. Associations were explored using multivariable regression models adjusted for confounders.

At baseline, prediabetes was associated with higher kidney impairment prevalence (17.8% vs. 13.7%; p < 0.001), lower eGFR and increased ACR. Each 1% increase in HbA1c was linked to a 4.6 mL/min/1.73 m² decrease in eGFR. Prediabetes remained independently associated with kidney impairment (OR 1.17; 95% CI: 1.03-1.34; p = 0.020) and lower eGFR (β = -0.76; 95% CI: -1.40 to -0.13; p = 0.019). At follow-up, prediabetes predicted further eGFR decline, and HbA1c increase was independently associated with eGFR decline.

HbA1c-defined prediabetes is independently associated with early renal impairment and accelerated kidney function decline. These findings support incorporating renal risk assessment in prediabetes and suggest HbA1c as a marker for chronic kidney disease prevention strategies.