Open Access Research article

An inverted J-shaped association of serum uric acid with muscle strength among Japanese adult men: a cross-sectional study

Cong Huang1, Kaijun Niu2, Yoritoshi Kobayashi1, Lei Guan1, Haruki Momma3, Yufei Cui1, Masahiro Chujo1, Atsushi Otomo1, Hui Guo1, Hiroko Tadaura1 and Ryoichi Nagatomi13*

Author Affiliations

1 Department of Medicine and Science in Sports and Exercise, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan

2 Department of Epidemiology, School of Public Health, Tianjin Medical University, 22 Qixiangtai Road, Heping District, Tianjin 300070, China

3 Division of Biomedical Engineering for Health and Welfare, Tohoku University Graduate School of Biomedical Engineering, 2-1 Seiryo-machi, Aoba-ku Sendai 980-8575, Japan

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BMC Musculoskeletal Disorders 2013, 14:258  doi:10.1186/1471-2474-14-258

Published: 30 August 2013

Abstract

Background

Uric acid (UA) may protect muscle function from oxidative damage due to reactive oxygen species through its powerful antioxidant capacity. However, several studies have demonstrated that hyperuricemia is closely related to systemic inflammation and has oxidant properties effects, both of which may increase the risk of muscle strength loss. The purpose of this study was to examine the association of serum UA concentration with grip strength and leg extension power in adult men.

Methods

This study is a cross-sectional survey in which 630 Japanese male employees aged 30 years and older participated. Five hundred and eighty-six subjects participated in the measurement of grip strength, and 355 subjects participated in the measurement of leg extension power. Blood samples were obtained for serum UA analysis.

Results

After adjustment for potential confounders, grip strength differed significantly between participants with and those without hyperuricemia (geometric mean and 95% confidence interval [CI]: 40.3 [39.2–41.3] kg vs. 41.9 [41.3–42.5] kg; P = 0.01). In addition, serum UA levels (quartiles) showed an inverted J-shaped curve with grip strength (mean and 95% CI: Q1, 41.6 [40.6–42.6] kg; Q2, 42.2 [41.2–43.2] kg; Q3, 41.8 [40.8–42.8] kg; Q4, 40.4 [39.3–41.4] kg; P for quadratic trend = 0.05). The results in the leg extension power group were similar to those observed in the grip strength group.

Conclusion

This population-based cross-sectional study shows for the first time that hyperuricemia is associated with poor muscle strength. Moreover, the results indicate an inverted J-shaped association between serum UA quartiles and muscle strength.

Keywords:
Grip strength; Leg extension power; Antioxidant; Reactive oxygen species; Inflammation