Non-albumin proteinuria is associated with all-cause mortality in community-dwelling adults

Non-albumin proteinuria (NAP), the presence of proteins other than albumin in urine, involves a wide range of urinary proteins that reflect mainly tubular injury. Although hospital-based studies have reported an association between NAP and mortality risk, little is known about this association in community-dwelling adults. This community-based prospective cohort study conducted in Japan included 6,601 participants (aged ≥ 40 years, 48.0% women). We assessed NAP as the difference between the urine albumin-to-creatinine ratio (ACR) and the urine protein-to-creatinine ratio. The association of NAP with all-cause mortality was assessed by multivariable Cox proportional hazard regression analysis, with adjustment for potential confounders. During the median follow-up of 11.2 years, a total of 1,182 deaths were documented. For a doubling of NAP, the adjusted hazard ratio (95% confidence interval) for mortality was 1.16 (1.11, 1.21). When further adjusted for ACR levels, this association remained significant (adjusted hazard ratio [95% confidence interval], 1.12 [1.06, 1.18]). We found that higher NAP was positively associated with all-cause mortality independent of albuminuria levels in community-dwelling adults. These findings suggest that NAP may serve as a complementary marker to albuminuria and is associated with elevated mortality risk in community settings.