Effect of osteosarcopenia on longitudinal mortality risk and chronic kidney disease progression in older adults.

Introduction: Chronic kidney disease (CKD) causes a progressive loss of muscle and bone mass, which frequently overlap with and affect clinical outcomes. However, the impact of sarcopenia, low bone mineral density (BMD; osteopenia or osteoporosis), and osteosarcopenia (sarcopenia and low BMD) on CKD progression is yet to be determined. We aimed to address these issues in patients with CKD without kidney replacement therapy (KRT).

Methods: This prospective cohort study included 251 outpatients aged ≥65 years with CKD without KRT enrolled in our hospital between June 2016 and March 2017. Sarcopenia was defined according to the 2014 criteria of the Asian Working Group for Sarcopenia (AWGS), and low BMD was defined as a T-score of ≤-1.0. The patients were divided into four groups: normal (no sarcopenia/normal BMD), only low BMD (no sarcopenia/low BMD), only sarcopenia (sarcopenia/normal BMD), and osteosarcopenia (sarcopenia/low BMD). The primary outcome was a composite of all-cause deaths, initiating KRT, and admissions owing to major adverse cardiovascular and cerebrovascular events (MACEs). The secondary outcome was a kidney composite outcome that included a 30 % reduction in creatinine-based estimated glomerular filtration rate (eGFR) and initiating KRT. The outcome risk was determined using the Cox regression models adjusted for potential confounders.

Results: Median age (25th-75th percentile) and eGFR of the outpatients (35 % women) were 76 (69-81) years and 32.1 (20.8-41.7) ml/min/1.73 m, respectively. During a median follow-up period of 5.2 years, there were 22 deaths, 117 30 % eGFR reductions, 48 KRTs, and 18 admissions owing to MACEs. The osteosarcopenia group rather than the only low BMD or only sarcopenia groups exhibited a higher risk of the primary (hazard ratio [HR]: 3.28, 95 % confidence interval [CI]: 1.52-7.08) and kidney composite (HR: 2.07, 95 % CI: 1.10-3.89) outcomes. Among the osteosarcopenia-related body compositions and physical functions, low handgrip strength (HGS) was strongly associated with a high risk of primary and kidney composite outcomes (HR: 2.44, 95 % CI: 1.46-4.08; HR: 1.48, 95 % CI: 0.97-2.24, respectively). The increase in HGS but not the body mass index, skeletal muscle mass index, or BMD was associated with lower risks of primary and kidney composite outcomes (HR: 0.93, 95 % CI: 0.89-0.98; HR: 0.96, 95 % CI: 0.92-0.99 per 1 kg, respectively).

Conclusions: Osteosarcopenia was associated with poor survival and kidney outcomes in older patients with CKD. Low HGS, which is common in patients with osteosarcopenia and CKD, was associated with increased mortality risk and kidney function decline. These findings can help the risk prediction and pathogenesis of the kidney-bone-muscle axis and improving muscle strength can help mitigate CKD progression.