Associations of Serum Zinc, Copper, and Zinc/Copper Ratio with Sleep Duration in Adults

The existing evidence on the relationships of serum zinc, copper, and zinc/copper ratio with sleep duration is limited and conflicting. The present cross-sectional study aimed to investigate these associations in general adults by utilizing data from the 2011-2016 National Health and Nutrition Examination Survey. The concentrations of zinc and copper were measured in serum samples. Sleep duration (self-reported usual sleep duration) was categorized as 7 h/night (short sleep duration), 7-8 h/night (optimal sleep duration), and 8 h/night (long sleep duration). Multinomial logistic regression models and restricted cubic splines were constructed to examine the associations of serum zinc, copper, and zinc/copper ratio with sleep duration. A total of 5067 adults were included. After multivariate adjustment, compared with the optimal sleep duration group, the odds ratios (ORs) (95% confidence intervals, CIs) in the long sleep duration group for the highest versus lowest quartile of serum zinc concentration and zinc/copper ratio were 0.61 (0.39-0.96) and 0.58 (0.38-0.89), respectively. Furthermore, among males, the OR (95% CI) of long sleep duration for the highest versus lowest quartile of serum copper concentration was 2.23 (1.15-4.32). Finally, the dose-response trends suggested that participants with optimal sleep duration had the highest serum zinc concentration and zinc/copper ratio and a slightly lower serum copper concentration. No significant association was found between serum zinc, copper concentrations and the zinc/copper ratio and short sleep duration. In conclusion, serum zinc and zinc/copper ratio were inversely related to long sleep duration in adults, while serum copper was positively associated with long sleep duration in males.