Association between C-reactive protein and sarcopenia: The National Health and Nutrition Examination Survey.

C-reactive protein (CRP), a clinical biomarker, is frequently used to evaluate the inflammatory status of the body. However, the association between CRP levels and sarcopenia among the general adult population in the USA is unknown. This study focused on assessing whether CRP levels were associated with sarcopenia. This cross-sectional study collected adult data of adults from the 2015 to 2018 National Health and Nutrition Examination Survey. Four-extremity total muscle mass was used to evaluate sarcopenia (appendicular lean mass). In addition, dual-energy X-ray absorptiometry was adopted to measure appendicular lean mass. The CRP levels were used to assess inflammation status. Odds ratios (OR) and 95% confidence intervals (95% CI) were determined using multivariable logistic regression to analyze the association between CRP levels and sarcopenia. A multivariable-adjusted restricted cubic spline model was built to plot OR curves at 4 knots. Among the 3710 participants involved in this study (average age, 39.4 [11.54] years; 1801 [48.5%] men), 352 (9.5%) displayed characteristics of sarcopenia, while 3358 (90.5%) did not. Compared with participates in the lowest quartile (Q1) of CRP level (Q1; ≤0.08 to ≤0.7), those in the highest quartile (Q4; ≤4.3 to ≤188.5) had an adjusted OR for sarcopenia of 2.74 (95% CI, 1.65-4.57; P < .001). Based on the multivariable restricted cubic spline model, CRP levels showed a nonlinear association with sarcopenia (P < .001). The adjusted OR of sarcopenia of 1.86 (95% CI, 1.37-2.51; P < .001) was determined by 2 piecewise regression models for those having the CRP level of 1.8. Based on subgroup analysis, CRP levels were related to sarcopenia in males (OR, 1.03; 95% CI, 1-1.05) and individuals aged <50 years (OR, 1.03; 95% CI, 1.01-1.05), drinking (OR, 1.02; 95% CI, 1-1.03), and body mass index ≥ 25 kg/m2 (OR, 1.02; 95% CI, 1-1.03). Our results indicated that CRP levels showed a nonlinear correlation with sarcopenia among adults in the US.