BACKGROUND

Although studies have focused on the relationship between serum essential elements and muscle mass or muscle strength, research on sex- and age-specific associations between any two of them was limited. The purpose of this study was to investigate the linear and nonlinear relationships between four serum essential elements, including copper (Cu), zinc (Zn), magnesium (Mg), and calcium (Ca), with muscle health, including appendicular skeletal muscle mass (ASM), grip strength and fat-to-muscle ratio (FMR) among Chinese adults, and to explore the differences in these associations according to sex and age.

METHODS

This study included participants aged 18 years or older who completed bioelectrical impedance analysis (BIA) and serological testing. ASM and grip strength were adjusted by dividing by body mass index (BMI). The multivariable linear regression, the subgroup analysis, and the restricted cubic spline (RCS) analysis were carried out. Linear trend tests and interaction tests were also conducted.

RESULTS

A total of 5389 community-dwelling adults were included in the study. In the multivariable linear regression, serum Cu was negatively correlated with ASM/BMI and grip strength/BMI (both P for trend < 0.001), while there was a significant positive correlation with FMR (P for trend < 0.001). Inversely, serum Zn was positively correlated with ASM/BMI and grip strength/BMI (both P for trend < 0.001), while there was a significant negative correlation with FMR (P for trend = 0.006). In the subgroup analysis of sex and age, serum Cu showed stronger negative associations with ASM/BMI (P for interaction = 0.001) and grip strength/BMI (P for interaction = 0.004) in younger adults and a stronger positive association with FMR (P for interaction < 0.001) in adult women. In the RCS analysis, a nonlinear and reverse L-shaped association was detected between serum Cu and FMR (P for nonlinear < 0.004), as well as serum Zn and grip strength/BMI (P for nonlinear = 0.043).

CONCLUSIONS

Elevated serum Cu levels are correlated with diminished muscle health, with variations observed across different age groups and genders. In contrast, increased serum Zn and Ca levels are associated with enhanced muscle health. Maintaining the balance of serum essential elements for preserving muscle health may be worthy of note. However, further research is warranted to validate the conclusions.