Association of inflammatory markers with muscle and cognitive function in early and late-aging older adults

Age-related loss in muscle and cognitive function is common in older adults. Numerous studies have suggested that inflammation contributes to the decline in physical performance and increased frailty in older adults. We sought to investigate the relationship of inflammatory markers, including CRP, IL-6, IL-10, TNF-α, TNFR1, and TNFR2, with muscle and cognitive function in frail early-aging and non-frail late-aging older adults. Secondary analysis of a cross-sectional study. Two hundred community-dwelling older men and women were included. They had been recruited in two groups based on age and functional status: 100 early-agers (age 65−75, who had poor functional status, and more co-morbidities) and 100 late-agers (older than 75 years, who were healthier and had better functional status). We assessed CRP, IL-6, IL-10, TNF-α, TNFR1, TNFR2, grip strength, Short Physical Performance Battery (SPPB) score, and cognitive function. We used correlation coefficients, partial correlations, and regression modeling adjusted for age, BMI, gender, and exercise frequency. The mean age in the two groups were 70.4 and 83.2, respectively. In regression models adjusting for age, BMI, gender and exercise frequency, early-agers demonstrated significant associations between inflammatory markers and outcomes. Each mg/dl of CRP was associated with (regression coefficient ± standard error) −0.6 ± 0.2 kg in grip strength (p = 0.0023). Similarly, each pg/mL of TNF-α was associated with −1.4 ± 0.7 (p = 0.0454), each 500 pg/mL of TNFR1 was associated with −1.9 ± 0.6 (p = 0.0008), and each 500 pg/mL of TNFR2 was associated with −0.5 ± 0.2 (p = 0.0098) in grip strength. Each 500 pg/mL of TNFR1 was associated with −0.4 ± 0.2 point in SPPB (p = 0.0207) and each pg/mL in IL-10 with 0.2 ± 0.1 point in MoCA (p = 0.0475). In late-agers, no significant correlation was found between any of the inflammatory markers and functional outcomes. In early-agers with frailty and more co-morbidities, the inflammatory markers CRP, TNF-α, TNFR1, and TNFR2 were associated with grip strength, TNFR1 was correlated with physical performance, and IL-10 was correlated with cognitive function. However, in healthier late-agers, no relationship was found between inflammatory markers and muscle or cognitive function. Our findings suggest presence of a relationship between inflammation and loss of muscle performance and cognitive function in frailer and sicker individuals, regardless of their chronological age.