Association between body composition and high-sensitivity C-reactive protein in older adults aged 65 years and above in 18 longevity areas in China

Objective: To understand the association between body composition and elevated high-sensitivity C-reactive protein (hs-CRP) in older adults aged ≥65 years in 18 longevity areas in China. Methods: Based on cross-sectional data from the 2021 China Healthy Ageing and Biomarkers Cohort Study. The information about the demographic characteristics, lifestyles, cognitive function, and disease history of the older adults were collected through face-to-face interviews. Body composition indicators (muscle mass, fat mass, body fat percentage, and visceral fat level) were measured using bioelectrical impedance analysis. Plasma hs-CRP levels were detected by immunoturbidimetry, with >3.0 mg/L indicating elevated hs-CRP. Multivariable logistic regression model was used to analyze associations between four body composition indicators and elevated hs-CRP, and restricted cubic spline models were used to evaluate dose-response relationships. Results: A total of 4 596 older adults aged (82.61±10.55) years, in whom 2 185 (47.5%) were men, were included in the study, and elevated hs-CRP was detected in 1 287 older adults (28.0%). After adjustment for confounders, Q₄ group showed 32.8% lower risk of elevated hs-CRP compared with Q₁ group in terms of muscle mass (OR=0.672, 95%CI: 0.518-0.869). In contrast, Q₄ group showed 54.7% (OR=1.547, 95%CI: 1.189-2.012), 43.2% (OR=1.432, 95%CI: 1.141-1.799), and 73.8% (OR=1.738, 95%CI: 1.358-2.226) higher risks for elevated hs-CRP compared with Q₁ group in terms of fat mass, body fat percentage and visceral fat level. Restricted cubic spline models revealed significant nonlinear relationships between four body composition indicatos and risk for elevated hs-CRP (all P<0.05). Subgroup analysis indicated sex-specific associations: in men, Q₄ group showed reduced hs-CRP elevation risk by 43.7% in terms of muscle mass (OR=0.563, 95%CI: 0.408-0.774) with no significant association in terms of fat mass, and in women, Q₄ group showed increased risk by 82.5% in terms of fat mass (OR=1.825, 95%CI: 1.243-2.678) with no significant association in terms of muscle mass. Conclusions: Higher muscle mass might mitigate inflammation risk, while increased fat mass, body fat percentage, and visceral fat level might exacerbate the risk in older adults. Better body composition could help reduce systemic inflammation risk, but sex-specific difference exists.