The association between C-reactive protein to hemoglobin ratio and sarcopenia among elderly adults: a nationwide population-based study using data from the CHARLS study

Objectives This study aimed to investigate the association between the C-reactive protein to hemoglobin (CRP/Hb) ratio and sarcopenia, and evaluate the potential of this ratio as a screening biomarker for sarcopenia in older Chinese adults. Methods A nationwide population-based cross-sectional study was conducted using data from the 2015 wave of the China Health and Retirement Longitudinal Study (CHARLS). A total of 7735 participants aged ≥ 60 years were included. Sarcopenia was diagnosed according to the 2019 diagnostic criteria of the Asian Working Group for Sarcopenia (AWGS), which requires both low appendicular skeletal muscle mass (ASM) and either reduced muscle strength or impaired physical performance. The CRP/Hb ratio was calculated as the ratio of CRP (mg/L) to Hb (g/dL). Multivariate logistic regression models were used to assess the independent association between the CRP/Hb ratio and sarcopenia, adjusting for demographic characteristics, lifestyle factors, comorbidities, and other biochemical markers. Subgroup analyses (stratified by BMI, chronic lung disease, and mild physical activity) and receiver operating characteristic (ROC) curves were performed to explore the modified effect and predictive value of the CRP/Hb ratio for sarcopenia. Results The prevalence of sarcopenia in the study population was 14.3% (1109/7735). After adjusting for potential confounders, the CRP/Hb ratio was significantly and positively associated with the risk of sarcopenia (adjusted OR = 1.347, 95% CI: 1.005–1.806, P = 0.047). Subgroup analyses showed that this association was significant in participants with normal BMI (18.5–23.9 kg/m², OR = 1.423, P = 0.035), those with chronic lung disease (OR = 2.078, P = 0.017), and those engaging in mild physical activity (OR = 1.420, P = 0.046). ROC curve analysis indicated that the CRP/Hb ratio had a higher predictive value for sarcopenia (AUC = 0.464) compared with CRP alone (AUC = 0.447) or Hb alone (AUC = 0.356). Fitting analysis revealed a non-linear relationship between the CRP/Hb ratio and sarcopenia. Conclusions The CRP/Hb ratio is independently and positively associated with sarcopenia in Chinese adults aged ≥ 60 years. This ratio shows better predictive performance than single CRP or Hb, and may serve as a convenient and accessible screening biomarker for identifying high-risk populations of sarcopenia in clinical and public health settings. Future longitudinal studies are needed to confirm the causal relationship and validate its clinical utility.