Prevalence of abnormal albuminuria and specifically mildly increased albuminuria in people aged 45 and over in a Mediterranean population with a stratified analysis for diabetes and hypertension

Background. Albuminuria is recognized as an early marker of kidney injury, an independent predictor of cardiovascular events, and mortality. Yet the frequency of abnormal albuminuria (AA; UACR ≥ 30 mg/g) and specifically mildly increased albuminuria (MIA; 10–29 mg/g) in Mediterranean populations is still poorly characterized. Methods. A cross-sectional, multicentre study including all urine albumin-to-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) records from July 1, 2021, to June 30, 2023, in individuals ≥ 45 years [23,859 adults (median age 64 years; 54 % women)] within a Health Management Area was done. We used KDIGO 2024 classification, adding a new sub-category for MIA. Prevalence with 95 % confidence intervals (CI) was calculated and stratified by sex, age, diabetes, and hypertension. Findings. The overall prevalence of AA was 9.2 % (95 % CI 8.8–9.6), higher in men (10.8 %) than in women (7.9 %) and rose steadily with age: 3.9 % (45–59 y), 8.5 % (60–74 y), and 18.1 % (≥ 75 y). AA reached 18.8 % among those with diabetes and 22.7 % in diabetes plus hypertension, versus 6.8 % in only hypertensive people, and 1.5 % without both conditions. An inverse relationship with kidney function was observed (4.0 % in stage G1 versus 55.5 % in G4–G5). MIA was present in 8.7% (95% CI 8.4–9.0), showing similar distribution patterns at lower magnitudes; but a peak of 16.7 % occurred at eGFR 30–44 mL/ min/1.73 m², falling in G4–G5. Interpretation. Abnormal and mildly increased albuminuria affect nearly one in five adults aged 45 and over in Mediterranean primary care. Given its strong association with age, diabetes, hypertension, and declining kidney function, systematic UACR screening- including for MIA- must be prioritized to enable early detection and intervention.