Chronic inflammation is associated with low physical function in older adults across multiple comorbidities

Abstract

Background: Chronic subclinical inflammation may contribute to impaired physical function in older adults; however, more data are needed to determine whether inflammation is a common mechanism for functional decline, independent of disease or health status.

Methods: We examined associations between physical function and inflammatory biomarkers in 542 older men and women enrolled in four clinical studies at Wake Forest University between 2001 and 2006. All participants were at least 55 years and had chronic obstructive pulmonary disease, congestive heart failure, high cardiovascular risk, or self-reported physical disability. Uniform clinical assessments were used across studies, including grip strength; a Short Physical Performance Battery (SPPB; includes balance, 4-m walk, and repeated chair stands); inflammatory biomarker assays for interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), and C-reactive protein (CRP); and anthropometric measures.

Results: Higher levels of CRP and IL-6, but not TNF-alpha, were associated with lower grip strength and SPPB scores and longer times to complete the 4-m walk and repeated chair stands tests, independent of age, gender, and race. More importantly, these relationships were generally independent of disease status. Further adjustment for fat mass, lean mass, or percent body fat altered some of these relationships but did not significantly change the overall results.

Conclusions: Elevated CRP and IL-6 levels are associated with poorer physical function in older adults with various comorbidities, as assessed by a common battery of clinical assessments. Chronic subclinical inflammation may be a marker of functional limitations in older persons across several diseases/health conditions.

Figure 1.

Changes in physical function measures per 1 SD increment in log(CRP) after adjustment for age, gender, and race. In the combined analyses, coefficients are also adjusted for study. The p values are from the test for slope = 0 in the combined analyses. The size of the symbol is proportional to the sample size. A positive coefficient for chair rise and walk times and a negative coefficient for SPPB scores and grip strength are indicative of poorer physical function. CRP = C-reactive protein; PIE = Pharmacological Intervention in the Elderly; POWER = Power Training in Older Adults; REACT II = Reconditioning Exercise And COPD Trial II; SPPB = Short Physical Performance Battery; TRAIN = Trial of ACE Inhibition and Novel Cardiovascular Risk Factors.

Figure 2.

Changes in physical function measures per 1 SD increment in log(IL-6) after adjustment for age, gender, and race. In the combined analyses, coefficients are also adjusted for study. The p values are from the test for slope = 0 in the combined analyses. A positive coefficient for chair rise and walk times and a negative coefficient for SPBB scores and grip strength are indicative of poorer physical function. IL = interleukin-6; PIE = Pharmacological Intervention in the Elderly; POWER = Power Training in Older Adults; REACT II = Reconditioning Exercise And COPD Trial II; SPPB = Short Physical Performance Battery; TRAIN = Trial of ACE Inhibition and Novel Cardiovascular Risk Factors.

Figure 3.

Changes in physical function measures per 1 SD increment in log(TNF-α) after adjustment for age, gender, and race. In the combined analyses, coefficients are also adjusted for study. The p values are from the test for slope = 0 in the combined analyses. The size of the symbol is proportional to the sample size. A positive coefficient for chair rise and walk times and a negative coefficient for SPPB scores and grip strength are indicative of poorer physical function. PIE = Pharmacological Intervention in the Elderly; POWER = Power Training in Older Adults; REACT II = Reconditioning Exercise And COPD Trial II; SPPB = Short Physical Performance Battery; TNF = tumor necrosis factor alpha; TRAIN = Trial of ACE Inhibition and Novel Cardiovascular Risk Factors.