Sex- and age-differences in blood manganese levels in the US general population: national health and nutrition examination survey 2011-2012

Background: Manganese is an essential element, but excessive manganese exposure has neurotoxic effects. Objective: To examine blood manganese levels in the general population with respect to sex, age, race/ethnicity, pregnancy and menauposal status, as well as levels of trace elements in blood. Methods: We used data from the National Health and Nutrition Examination Survey, a national survey of U.S. residents (n = 7720 participants, ages 1 to 80 years). General linear models and generalized additive models were used to examine the association between blood manganese concentration and participants' characterisics, accounting for the complex survey design. Results: Blood manganese levels ranged from 1.6 to 62.5 mu g/L, with arithmetic means of 10.6 and 9.2 mu g/L for women and men, respectively. The following characteristics were significantly associated with higher blood manganese levels: female sex, younger age, Asian origin, and being pregnant. In addition, there were non-linear relationships between blood manganese levels and cadmium, iron, lead, and mercury levels. Conclusion: The higher blood manganese levels observed among females suggest sex-related metabolic differences in the regulation of manganese, and elevated levels among pregnant women suggest an important role of manganese in reproduction. The present study supports the need to take into consideration age- and sex-related differences in blood manganese levels, as well as pregnancy status when examining manganese essentiality or toxicity.