Associations Between Surrogates of Skeletal Muscle Mass and History of Bone Fracture in Patients with Chronic Kidney Disease: The Fukuoka Kidney disease Registry (FKR) Study

Patients with chronic kidney disease (CKD) are at increased risks of both sarcopenia and fragility fractures. However, information on the association between skeletal muscle mass (SMM) and the risk of bone fractures in patients with CKD is lacking. We performed a cross-sectional analysis of 4146 patients with CKD using the baseline dataset of the Fukuoka Kidney disease Registry Study, as a multicenter, prospective cohort study of pre-dialysis CKD patients. The main measure was estimated SMM (eSMM) calculated using an equation validated by bioelectrical impedance analysis with two independent datasets of 100 and 81 CKD patients. The main outcome was historical bone fractures. The associations between sex-specific quartiles (Q1-Q4) of eSMM and fracture history were assessed by logistic regression analyses. The prevalence of a history of fractures increased and eSMM decreased with progressive CKD stages. Among the 4146 patients, 249 had prior bone fractures, including 111 patients in Q1 (lowest quartile), 65 in Q2, 46 in Q3, and 27 in Q4 (highest quartile). A multivariable-adjusted model revealed that patients in Q1 had a significantly higher odds ratio (95% confidence interval) for bone fracture history than those in Q4 (reference): Q1, 2.77 (1.32-5.80); Q2, 1.95 (1.05-3.65); and Q3, 1.57 (0.90-2.75) (P-value for trend < 0.001). Similar associations were obtained when other skeletal muscle surrogates were applied: serum creatinine to serum cystatin C and daily urinary creatinine excretion. These results suggest that a lower eSMM is associated with an increased prevalence of historical bone fractures in pre-dialysis CKD patients.