Inflammation in Relation to Sarcopenia and Sarcopenic Obesity among Older Adults Living with Chronic Comorbidities: Results from the National Health and Nutrition Examination Survey 1999–2006

Loss of muscle mass and waning in muscle strength are common in older adults, and inflammation may play a key role in pathogenesis. This study aimed to examine associations of C-reactive protein (CRP) and systemic immune-inflammation index (SII) with sarcopenia and sarcopenic obesity in older adults with chronic comorbidities. Cross-sectional data from the National Health and Nutrition Examination Survey (1999-2006) were obtained for participants aged ≥60 years. Sarcopenia was defined by a lean mass and body height (males < 7.26 kg/m², females < 5.45 kg/m²). Sarcopenic obesity was defined by the concurrent presence of sarcopenia and obesity (defined by relative fat mass). Logistic regression was used to assess the associations of CRP and SII with sarcopenia and sarcopenic obesity. The dose-response relationship was examined via restricted cubic splines. Of the participants (<i>n</i> = 2483), 23.1% (<i>n</i> = 574) and 7.7% (<i>n</i> = 190) had sarcopenia and sarcopenic obesity, respectively. The multivariable logistic regression models suggested a positive association of SII with sarcopenia and sarcopenic obesity, but a positive statistically significant association was not consistently observed for CRP. Dose-response curves suggested similar association patterns for these biomarkers. In clinical practice, measures to prevent sarcopenia and sarcopenic obesity are needed for older vulnerable people with high systemic inflammation.