Association between blood cell inflammatory indices and sarcopenic obesity in middle-aged and older Chinese adults: a cross-sectional study

Background & aims: Despite the known association between chronic inflammation and reduced muscle mass, the use of inflammatory indices in sarcopenic obesity (SO) remains unexplored. Thus, this study aimed to explore the relationship between blood cell inflammatory indices and SO and assess their potential role in disease evaluation and monitoring. Methods Methods: This cross-sectional study included 1,009 participants aged ≥ 50 years. SO was defined by the presence of both sarcopenia (muscle mass < 39.3% for men or < 33.9% for women) and obesity [defined as body mass index (BMI) ≥ 28 kg/m², body fat percentage (PBF) ≥ 30% for men or ≥ 40% for women, visceral fat area (VFA) ≥ 100 cm², or waist circumference (WC) ≥ 80 cm for women and ≥ 90 cm for men]. Inflammatory indices, including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), platelet-to-white blood cell ratio (PWR), systemic immune-inflammatory index (SII), systemic inflammation response index (SIRI), and aggregate inflammation systemic index (AISI), were calculated from routine blood tests. ANOVA and regression analyses were used to examine the relationship between these indices and SO. Results When the WC classification was used, risk of SO was significantly associated with the SIRI (OR = 1.361, 95% CI, 1.057–1.753; P  = 0.017) and AISI (OR = 1.248, 95% CI, 1.022–1.524; P  = 0.029), but negatively correlated with PWR (OR = 0.621, 95% CI: 0.390–0.988, P  = 0.040). The results were similar for the VFA classification. When the BMI ≥ 28 kg/m² classification was used, risk of SO was significantly associated with SIRI (OR = 1.539, 95% CI: 1.133–2.092, P  = 0.006) and AISI (OR = 1.374, 95% CI: 1.066–1.771, P  = 0.014). However, when the PBF classification was used, blood cell inflammatory indices and risk of SO were not significantly correlated. Conclusions The correlation between systemic immune inflammation indices and SO may be influenced by the SO classification method. Owing to their advantages of being objective, low-cost, and easy-to-use markers, SIRI, AISI, and PWR may serve as biomarkers for the screening and management of SO when classified by WC, VFA, or BMI ≥ 28 kg/m².