Serum C-Reactive Protein Even at Very Low (< 1.0 mg/l) Concentration Is Associated with Physical Performance in a Community-Based Elderly Population Aged 70 Years and Over

Background: Although several studies have reported that C-reactive protein (CRP) is associated with physical performance, few studies have evaluated the relationships between CRP and physical performance among subjects who had a very low range of CRP. Therefore, it is still unclear whether a lower CRP is favorably associated with physical performance even within a very low range. Objective: The aim of this study was to investigate the relationships between CRP and physical performance among a Japanese population with a low serum CRP concentration (CRP <1.0 mg/l). Methods: We designed a cross-sectional survey for 775 persons aged 70 years and older living in Japan. High-sensitivity CRP was measured using a nephelometric method. The subjects whose serum CRP concentrations were higher than 10.0 mg/l were excluded. Physical performance was assessed using a 10-meter maximum walk test, leg extension power, and a timed 'up and go' test. Results: The median value ( interquartile range) of CRP was 0.55 (0.29-1.20) mg/l. After adjustment for potential confounding factors, an inverse relation of CRP with the 10-meter maximum walk test and leg power was observed in all subjects (p for trend = 0.10 and 0.04, respectively). For subjects who had a CRP <1.0 mg/l, these inverse relations were unchanged (p for trend = 0.03 and 0.02, respectively). Conclusions: Serum CRP concentration is favorably related to physical performance, even within a very low range in a community-based elderly population aged 70 years and over. The findings suggest that maintaining as low CRP levels as possible may potentially maintain better physical performance. Copyright (C) 2008 S. Karger AG, Basel