The association of mixed multi-metal exposure with sleep duration and self-reported sleep disorder: A subgroup analysis from the National Health and Nutrition Examination Survey (NHANES)

Sleep disorders significantly affect sleep duration and constitute a major public health issue. However, the relationship between metal exposure and sleep is not fully elucidated. This study utilized publicly available data from the National Health and Nutrition Examination Survey (NHANES) to measure blood concentrations of seven metals-copper (Cu), zinc (Zn), selenium (Se), manganese (Mn), mercury (Hg), cadmium (Cd), and lead (Pb)-in a cohort of 4263 American adults. The relationship between metal exposure and self-reported sleep duration and sleep disorder risk was analyzed using single exposure models like logistic and linear regression and mixedexposure models such as weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR). The results indicated an absence of statistically significant findings in the single exposure model. In contrast, the mixed exposure model revealed a positive correlation between selenium levels and the risk of sleep disorders across the entire population. A "U-shaped" association was identified between copper levels and the risk of sleep disorders in males, females, and individuals aged 60 and above. Moreover, a positive trend was observed between manganese levels and the risk of sleep disorders in individuals aged 60 and above. Additionally, elevated concentrations of metal mixtures were significantly associated with reduced sleep duration among females. Sensitivity analyses corroborated these findings. In conclusion, within the context of metal mixtures, selenium may be a risk factor for sleep disorders in the general population. Manganese may be a unique risk factor in older adults. Copper levels have a "U" shaped link to sleep disorder risk in specific population subgroups. Finally, the accumulation of blood metal mixtures in females, mainly due to lead and mercury, may reduce sleep duration. Further research is necessary to validate these findings.