Association Between Dietary Copper Intake and Incident Metabolic Syndrome in Chinese Adults: A Discrete-Time Hazard Model Analysis

Objective: The aim of this study was to examine the association between dietary copper intake and incident metabolic syndrome (MetS) in Chinese adults. Methods: Data were obtained from the China Health and Nutrition Survey (CHNS) in 2009, 2015, and 2018. A total of 2418 adults aged 18–64 years who were free of MetS at baseline in 2009 were included. Person-period data were constructed, and discrete-time hazard models with a complementary log-log link were used to evaluate the associations of dietary copper intake with incident MetS and its components. Restricted cubic spline analysis (RCS) was used to assess the dose–response relationship. Results: After multivariable adjustment, compared with the lowest quartile (Q1) of dietary copper intake, the Q4 groups had a higher risks of incident MetS, with HR (95% CI) of 1.32 (1.06–1.65) (p = 0.014). When analyzed as a continuous variable, each 1 mg/1000 kcal increase in energy-adjusted dietary copper intake was associated with an approximately 27% higher risk of incident MetS (HR = 1.27, 95% CI: 1.03–1.53) (p = 0.023). RCS indicated a significant overall association without evidence of nonlinearity. Component analyses suggested that higher dietary copper intake might be associated with increased risks of reduced high-density lipoprotein cholesterol (HDL-C) and abdominal obesity. Sensitivity analyses were generally consistent with the main findings. Conclusions: Higher dietary copper intake was associated with an increased risk of incident MetS in Chinese adults. Component analyses suggested a more consistent association for reduced HDL-C, while an additional possible association was observed for abdominal obesity.