Results Twenty-nine studies have been found from the referred theme. Several studies have been performed in animal models. Only three papers reported the effects of metals on sleepwake cycle. The first one was carried out with a population living in the surroundings of a metal recycling plant, where authors have detected that the exposed population had 2.3 chances to report sleep complaints. The other two studies observed children and pre-teens with high levels of lead in the blood have been

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... ociated to delay in the onset of sleep, longer duration of nocturnal awakenings, shorter duration of sleep, insomnia (OR=2.01) and longer daytime sleepiness (OR=2.90). Discussion There are effects which link the environmental exposure to lead and cadmium with sleep complaints. Considering there are several production sectors, such as mining, and manufacturing processing industries that work with such metals and whose workers are in continuous shifts, it is likely that workers in these industries may suffered the effects of metal exposure and those leading to changes in biological rhythms caused by shift work. Financial Support: Faperj (E-10/225.935/2016).