#2439 The association between vitamin D deficiency and sarcopenia in patients with pre-dialysis CKD

Abstract Background and Aims Sarcopenia is characterized by a progressive and widespread loss of skeletal muscle, leading to muscle weakness and frailty. While primary sarcopenia is linked to aging, secondary sarcopenia can independently occur, especially in chronic conditions like chronic kidney disease (CKD). Investigating sarcopenia in CKD patients has become a focal point in research due to its significant impact on the quality of life, morbidity, and mortality of these individuals. Despite reports connecting vitamin D deficiency, prevalent in CKD, to sarcopenia in the general population, there is limited information regarding the specific relationship between vitamin D and sarcopenia in CKD. This study aims to explore the association between vitamin D deficiency and sarcopenia in patients with pre-dialysis CKD. Method This cross-sectional study enrolled 569 patients with pre-dialysis chronic kidney disease (CKD), defined as having an estimated glomerular filtration rate (eGFR) less than 60 ml/min/m2. Sarcopenia was assessed using computed tomography (CT)-derived skeletal muscle index (SMI), calculated based on the cross-sectional area of skeletal muscles at the 3rd lumbar vertebra. Using Korean-specific SMI cutoffs, patients were categorized into sarcopenic and non-sarcopenic groups. Logistic regression analyses were employed to explore associations between sarcopenia and baseline variables, including active vitamin D, specifically 1,25-dihydroxyvitamin D [1,25(OH)2D] level. Results Among the 569 patients, 278 had CKD stage 3, 198 had CKD stage 4, and 93 had CKD stage 5. The prevalence of sarcopenia increased with advancing CKD stage (CKD stage 3 vs. stage 4 vs. stage 5: 20.1% vs. 31.3% vs. 41.9%, P < 0.001). Univariate logistic regression analysis revealed an association between 1,25(OH)2D levels and sarcopenia. Additionally, age, male sex, diabetes, body mass index, eGFR, urinary albumin excretion levels, and serum levels of albumin, high-sensitive C-reactive protein (hsCRP), and intact parathyroid hormone were associated with sarcopenia. In multivariable logistic regression analysis, 1,25(OH)2D levels remained independently associated with sarcopenia (per 1 pg/dl increase, odds ratio [OR]: 0.84; 95% confidence interval [CI]: 0.80–0.87, P < 0.001). Age (per 1 year increase, OR: 1.04, 95% CI: 1.02–1.07, P < 0.001), diabetes (vs. non-diabetes, OR: 2.33, 95% CI: 1.39–3.89, P = 0.001), serum albumin (per 1 mg/dl increase, OR: 0.39, 95% CI: 0.22–0.71, P = 0.0023), and hsCRP (per 1 mg/dl increase, OR: 1.91, 95% CI: 1.25–2.92, P = 0.003) were also independently associated with sarcopenia. Conclusion This study revealed an independent association between 1,25(OH)2D levels and sarcopenia derived from CT scans in pre-dialysis CKD patients. This association retained significance even after adjusting for traditional risk factors for sarcopenia, such as age, diabetes, serum albumin, and hsCRP. Further prospective studies are necessary to determine whether therapy with exogenous 1,25(OH)2D drugs can improve sarcopenia in these patients.