Risk of proteinuria among individuals with persistent borderline diabetes: the Saku study.

Objective: To investigate the risk of decreased estimated glomerular filtration rate (eGFR) and proteinuria among individuals with borderline diabetes.

Methods: This 5-year cohort study involved 2849 participants aged 30-79 years without diabetes or chronic kidney disease at baseline (April 2008-March 2009). Participants were categorized into two groups-normoglycemia and borderline diabetes-based on the results of a 75-g oral glucose tolerance test at baseline. Participants underwent annual comprehensive medical check-ups during the follow-up period until March 2014. Main outcomes were defined as proteinuria ≥[1+] or eGFR <60 ml/min/1.73 m2. Cox proportional hazards regression was used to estimate the hazard ratio (HR) and 95 % confidence interval (CI) of eGFR <60 ml/min/1.73 m2 and proteinuria ≥[1+] for the borderline diabetes group compared with the normoglycemia group.

Results: During the follow-up period, 335 individuals developed eGFR <60 ml/min/1.73 m2 and 136 individuals developed proteinuria ≥[1+]. Participants in the borderline diabetes group did not have a significantly higher risk of eGFR <60 ml/min/1.73 m2 or proteinuria ≥[1+] after multivariable adjustment. However, participants with borderline diabetes who were also diagnosed with borderline diabetes at the endpoint examination had a significantly higher risk of proteinuria ≥[1+] compared with participants with normoglycemia who also had normoglycemia at the endpoint examination; the HR (95 % CI) was 1.76 (1.11-2.78).

Conclusions: Persistent borderline diabetes significantly increases the risk of proteinuria.