Summary: Bone disorder is a common complication of chronic kidney disease (CKD). The clinical usefulness of bone mineral density (BMD) in CKD is not well known. Our study shows that low BMD is associated with physical activity and dietary Na/K intake ratio and can predict poor renal outcome in non-dialysis CKD.
Purpose: Despite evidence of a link between bone mineral disorders and chronic kidney disease (CKD), the clinical implications of bone mineral density (BMD) in CKD are not well established. We investigated risk factors and renal outcomes of low BMD in CKD.
Methods: We analyzed data from the KNOW-CKD. BMD measured by dual-energy x-ray absorptiometry was classified by T score: normal (T score ≥ − 1.0), osteopenia (− 1.0 > T score > − 2.5), and osteoporosis (T score ≤ − 2.5) of the lumbar spine, hip, or femoral neck. Logistic regression analysis to assess risk factors of low BMD (T score < − 1.0) and Cox proportional hazards models to estimate risk of incident end-stage renal disease (ESRD).
Results: Low BMD was prevalent (osteopenia 33%; osteoporosis 8%) in 2128 adults with CKD (age 54 ± 12 years; male 61%). Over a median follow-up of 4.3 years, there were 521 cases of incident ESRD. Lower BMD was associated with female sex, older age, low eGFR, low BMI, and lifestyle factors of physical activity (odds ratio (OR) = 0.62, 95% confidence interval (0.49–0.77)) and spot urine Na/K ratio (1.07 (1.00–1.15)). In adjusted Cox models, low BMD was associated with increased incident ESRD (hazard ratio (HR) = 1.14 (0.92–1.41) for osteopenia; 1.43 (1.01–2.04) for osteoporosis, P for trend < 0.05) compared with the reference of normal BMD. The association between low BMD and ESRD was similar according to T score discordance classification.
Conclusions: Low BMD was associated with modifiable lifestyle factors including low physical activity and high dietary Na/K intake ratio. The presence of low BMD is associated with poor renal outcomes in non-dialysis CKD.