U-shaped nonlinear relationship between dietary copper intake and peripheral neuropathy

Abstract

Background: Dietary copper intake is a promising predictor of peripheral neuropathy. There is no research exploring the potential link between dietary copper intake and peripheral neuropathy. Methods: The information utilized in our research was collected from the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2004. The relationship between dietary copper intake and peripheral neuropathy was analyzed using a multivariate logistic regression model and restricted cubic spline (RCS). Results: The RCS analysis results showed a U-shaped nonlinear relationship between dietary copper intake and peripheral neuropathy (P for nonlinearity < 0.001). The threshold effect analysis results indicated that when dietary copper intake was less than 0.889 mg/d, the risk of peripheral neuropathy decreased with increasing copper intake (OR: 0.388, 95% CI: 0.200-0.753). When dietary copper intake was ≥ 0.889 mg/d, the risk of peripheral neuropathy increased with increasing copper intake (OR: 1.129, 95% CI: 1.006–1.266). And the incidence rate of peripheral neuropathy in the first quantile (OR: 1.421, 95% CI: 1.143–1.766), the third quantile (OR: 1.358, 95% CI: 1.057–1.744), and the fourth quantile (OR: 1.676, 95% CI: 1.250–2.248) of dietary copper intake were significantly higher than that in the second quantile (where the inflection point was located). Conclusion: Our study suggests that both insufficient and excessive dietary copper intake may be associated with an increased incidence of peripheral neuropathy. However, further research is needed to provide definitive evidence and confirm these findings.