Supplementary Material for: Low Skeletal Muscle Mass Predicts Incident Dipstick Albuminuria in Korean Adults without Chronic Kidney Disease: A Prospective Cohort Study

Background: Previous cross-sectional studies have shown that low muscle mass is associated with albuminuria in the general population. However, the longitudinal association of low muscle mass with the development of albuminuria is not well known at this time. Methods: We evaluated 48,101 individuals without chronic kidney disease (CKD) who underwent 2 health check-ups in 2012 and 2016. Participants’ skeletal muscle masses were measured using a bioelectrical impedance analyzer and compared via a skeletal muscle mass index (SMI; SMI [%] = total skeletal muscle mass [kg]/body weight [kg] × 100). Urine albumin was determined by dipstick semi-quantitative analysis and incident albuminuria was defined as ≥1+ dipstick albumin at the time of the second check-up. We used logistic regression analysis to determine the relationship between skeletal muscle mass and incident albuminuria. Results: The study participants were divided into quartiles according to baseline SMI. After 4 years, 305 cases of incident albuminuria were observed. The cumulative incidences of albuminuria were 0.78, 0.66, 0.62, and 0.47% for the first through fourth quartiles of SMI respectively. Multivariable logistic analysis revealed that the ORs (95% CIs) for incident albuminuria were 1.63 (1.05–2.55) in the first quartile compared with those in the fourth quartile and 1.40 (1.05–1.88) in the participants with sarcopenia versus those without sarcopenia. Conclusions: Low skeletal muscle mass was independently associated with the development of dipstick albuminuria after 4 years in Korean adults without CKD. Further research is needed to verify the role of low muscle mass in the development of albuminuria and renal injury.