Body Mass Index and the Risk of Persistent Proteinuria in Middle-Aged Men: The Kansai Healthcare Study

<b><i>Introduction:</i></b> Proteinuria is a risk factor for end-stage renal failure. However, it is not known whether body mass index (BMI) is prospectively associated with the risk of future developing proteinuria, taking into account transient proteinuria. <b><i>Methods:</i></b> We enrolled 9,320 nondiabetic Japanese middle-aged men who had no proteinuria, an estimated glomerular filtration rate ≥60 mL/min/1.73 m², no history of cancer, and no use of antihypertensive medications at baseline. “Any proteinuria” was defined as proteinuria detected for the first time during the follow-up period regardless of its frequency. “Persistent proteinuria” was defined as proteinuria that was detected at least twice consecutively at annual examinations and did not return to negative until the end of the follow-up. <b><i>Results:</i></b> During the 11-year follow-up period, 1,972 cases of any proteinuria and 151 cases of persistent proteinuria were confirmed. Both lower and higher BMI were associated with the risk of any proteinuria. As for persistent proteinuria, in those with a BMI ≥20 kg/m², higher BMI was associated with a higher risk of future persistent proteinuria. The association between BMI and the risk of persistent proteinuria was stronger than that between BMI and any proteinuria. In multiple-adjusted model, hazard ratios of persistent proteinuria for BMI &#x3c;18.0, 18.0–19.9, 20.0–21.9, 22.0–23.9, 24.0–25.9, 26.0–27.9, and ≥28.0 kg/m² were 1.52 (95% confidence interval 0.51–4.49), 1.07 (0.49–2.29), 1.00 (reference), 1.14 (0.64–2.01), 1.89 (1.09–3.27), 2.12 (1.15–3.93), and 3.85 (2.03–7.30), respectively. <b><i>Discussion/Conclusion:</i></b> In those with a BMI ≥20 kg/m², higher BMI was associated with a higher risk of future persistent proteinuria and any proteinuria. This relationship was stronger for persistent proteinuria than for any proteinuria.