Plasma inflammation-related biomarkers are associated with intrinsic capacity in community-dwelling older adults.

Abstract

How inflammation relates to intrinsic capacity (IC), the composite of physical and mental capacities, remains undefined. Our study aimed to investigate the cross-sectional and longitudinal associations between plasma inflammation-related biomarkers and IC in older adults. This secondary analysis of the Multidomain Alzheimer Preventive Trial (MAPT) included 1238 community-dwelling older individuals with IC assessments from 12 to 60months. Plasma C-reactive protein (CRP), interleukin-6 (IL-6), tumour necrosis factor receptor-1 (TNFR-1), monocyte chemoattractant protein-1 (MCP-1) and growth differentiation factor-15 (GDF-15) were measured at 12months. IC was operationalized as a score ranging from 0 to 100, derived from four domains: cognition, Mini-Mental State Examination; locomotion, Short Physical Performance Battery; psychological, Geriatric Depression Scale; and vitality, handgrip strength. A five-domain IC score (plus sensory) was investigated in a subsample (n=535) with a 1-year follow-up as an exploratory outcome. The mean age of the 1238 participants was 76.2years (SD=4.3); 63.7% were female. Their initial four-domain IC scores averaged 78.9 points (SD=9.3), with a yearly decline of 1.17 points (95% CI=-1.30 to -1.05; P<0.001). We observed significant associations of lower baseline IC with higher CRP, IL-6, TNFR-1 and GDF-15, after controlling age, sex, MAPT group allocation and educational level [CRP: adjusted β (95% CI)=-1.56 (-2.64 to -0.48); P=0.005; IL-6: adjusted β=-3.16 (-4.82 to -1.50); P<0.001; TNFR-1: adjusted β=-6.86 (-10.25 to -3.47); P<0.001; GDF-15: adjusted β=-7.07 (-10.02 to -4.12); P<0.001]. Higher TNFR-1, MCP-1 and GDF-15 were associated with faster decline in four-domain IC over 4years [TNFR-1: adjusted β (95% CI)=-1.28 (-2.29 to -0.27); P=0.013; MCP-1: adjusted β=-1.33 (-2.24 to -0.42); P=0.004; GDF-15: adjusted β=-1.42 (-2.26 to -0.58); P=0.001]. None of the biomarkers was significantly associated with the five-domain IC decline. Inflammation was associated with lower IC in older adults. Among all plasma biomarkers, TNFR-1 and GDF-15 were consistently associated with IC at the cross-sectional and longitudinal levels.