Elevated IL-6 and CRP levels are associated with incident self-reported major mobility disability: A pooled analysis of older adults with slow gait speed.

Background Elevated Interleukine-6 (IL-6) and C-reactive protein (CRP) are associated with aging-related reductions in physical function, but little is known about their independent and combined relationships with major mobility disability (MMD), defined as the self-reported inability to walk a quarter-mile. Methods We estimated the absolute and relative effect of elevated baseline IL-6, CRP, and their combination on self-reported MMD risk among older adults (≥68 years; 59% female) with slow gait speed ( Results We found higher MMD risk per unit increase in log IL-6 [HR=1.26 (95% CI 1.13 to 1.41)]. IL-6 meeting pre-determined threshold considered to be high (>2.5 pg/mL) was similarly associated with higher risk of MMD [HR=1.31 (95% CI: 1.12 to 1.54)]. Elevated CRP (CRP >3.0 mg/L) was also associated with increased MMD risk [HR=1.38 (95% CI: 1.10 to 1.74)]. The CRP effect was more pronounced among participants with elevated IL-6 [HR=1.62 (95% CI: 1.12 to 2.33)] compared to lower IL-6 levels [HR=1.19 (95% CI: 0.85 to 1.66)]. Conclusions High baseline IL-6 and CRP were associated with increased risk of MMD among older adults with slow gait speed. A combined biomarker model suggests CRP was associated with MMD when IL-6 was elevated.