Inflammatory markers and physical performance in older persons: the InCHIANTI study.

BACKGROUND: Some studies have proposed chronic inflammation as an underlying biological mechanism responsible for physical function decline in elderly people. The aim of this study is to evaluate the relationship between several inflammatory markers and physical performance in an older population.
METHODS: This study is part of the "Invecchiare in Chianti" (InCHIANTI) study, a prospective population-based study of older people, aimed at identifying risk factors for late-life disability. The study sample consisted of 1020 participants aged 65 years and older living in the Chianti area of Italy. Physical performance was assessed using walking speed, the chair-stand test, and the standing balance test. Hand-grip strength was assessed using a hand-held dynamometer. Serum levels of C-reactive protein (CRP), interleukin (IL)-6, tumor necrosis factor-alpha (TNF-alpha), IL-10, IL-1beta, IL-6sR, and IL-1RA were determined. Linear regression analyses were used to assess the multivariate relationship of inflammatory marker levels with physical performance, scored as a continuous variable from 0 to 3, and hand-grip strength after adjustment for demographics, chronic conditions, medication use, and other biological variables.
RESULTS: CRP, IL-6, and IL1RA were significantly correlated with physical performance (r=-0.162, r=-0.251, and r=-0.127, respectively). Significant correlations with hand-grip strength were found for CRP and IL-6 (r=-0.081 and r=-0.089, respectively). After adjustment for covariates, high levels of IL-6 and IL-1RA continued to be strongly associated with worse physical performance (p<.001 and p=0.004, respectively). High levels of CRP (p<.001) and IL-6 (p<.001) were associated with low hand-grip strength. Mean adjusted physical performance scores ranged from 2.21 in the CRP<0.59 mg/dl group to 2.07 in the CRP>0.60 mg/dl group (p for trend=.004), and from 2.25 in the lowest IL-6 quartile to 2.08 in the highest IL-6 quartile (p for trend<.001). This trend was also reflected in mean adjusted hand-grip strength, with a range from 28.8 kg for the CRP<0.59 mg/dl group to 26.0 kg for the CRP>0.60 mg/dl group (p for trend=.001), and from 27.4 kg for the lowest IL-6 quartile to 25.1 kg for the highest IL-6 quartile (p for trend=.001).
CONCLUSIONS: Inflammation, measured as high levels of IL-6, CRP, and IL-1RA, is significantly associated with poor physical performance and muscle strength in older persons. These data also support the biological face validity of physical performance measures. The assessment of inflammatory markers may represent a useful screening test and perhaps a potential target of intervention.