Associations of a metal mixture and vitamin D with sleep duration among adolescents and young adults from the 2011-2018 NHANES cycles

Introduction: Heavy metal exposure has been associated with poor sleep, but little is known about the cumulative associations of multiple metals with sleep duration, particularly among adolescents. This study examined the association of blood lead (Pb), cadmium (Cd), and mercury (Hg) concentrations with sleep duration and possible effect modification by vitamin D. Methods: The study sample consisted of 16-25-year-olds (n = 2637) from the 2011-2018 National Health and Nutrition Examination Survey. The association of each blood metal and serum vitamin D level with self-reported sleep duration was examined through linear regression models. Interaction terms and stratified models tested the effect modification of metal association with sleep by vitamin D level or status. Cumulative and interactive associations among the metals and serum vitamin D were also estimated using Bayesian Kernel Machine Regression (BKMR). Results: In linear regressions, there was little evidence of an association between individual metals, vitamin D level, and sleep duration. Both linear regressions and BMKR models showed little indication of interactions among metals and vitamin D levels. BKMR results suggested an overall joint association, with longer sleep duration at higher percentile of the metal-vitamin D mixture (75th percentile vs 50th: beta=0.07 hours; 95 % CrI: 0.01, 0.13). Conclusion: In the context of low-level metal exposure, individual metals were unrelated to sleep duration. We found some evidence that higher levels of the mixture of blood Pb, Cd, Hg, and serum vitamin D level may be associated with slightly longer sleep duration, underscoring the importance of considering multiple environmental exposures. Additional analyses, especially in higher risk groups (e.g., higher exposures; higher prevalence or severity of vitamin D deficiency) are warranted.