Association Between Blood Heavy Metal Exposure and Sleep Duration Among Korean Adults: Data From the Korea National Health and Nutrition Examination Survey, 2005–2017

Objectives: We evaluated the associations between blood mercury (Hg), lead (Pb), and cadmium (Cd) concentrations and sleep duration among Korean adults and explored whether these associations differed across subgroups.Methods: This cross-sectional study included 17,831 adults aged ≥20 years from the Korea National Health and Nutrition Examination Survey (KNHANES 2005–2017). Sleep duration was assessed using self-reported data. Associations between blood heavy metal concentrations and sleep duration were examined using complex-sample multiple linear regression, accounting for the survey design with adjustments for sociodemographic and health-related covariates.Results: In the covariate-adjusted models, higher blood concentrations of Hg, Pb, and Cd were significantly associated with shorter sleep duration. Sleep duration decreased by 0.113 hours per 10 μg/L increase in Hg (95% confidence interval [CI]: -0.183 to -0.043; p=0.002), 0.076 hours per 1 μg/dL increase in Pb (95% CI: -0.098 to -0.054; p<0.0001), and 0.106 hours per 1 μg/L increase in Cd (95% CI: -0.146 to -0.066; p<0.0001). Subgroup analyses suggested that the magnitude of the associations varied according to sex and work type, with stronger inverse associations observed among female participants and shift workers.Conclusions: Higher blood heavy metal concentrations are inversely associated with sleep duration among Korean adults. These findings suggest that environmental exposure may be related to sleep quantity. Further longitudinal studies incorporating objective sleep measures are needed to clarify the temporal relationships and underlying mechanisms.