New York, Nov 14 (IANS): Lead exposure in early in life is associated with increased risk of sleep problems and excessive daytime sleepiness in later childhood, says a new study.

"Little is known about the impact of heavy metals exposure on children's sleep, but the study's findings highlight that environmental toxins - such as lead - are important pediatric risk factors for sleep disturbance," said the study's principal investigator Jianghong Liu, associate professor at University of Pennsylvania School of Nursing.

"Lead exposure is preventable and treatable, but if left unchecked can result in irreversible neurological damage," Liu noted.

Lead can be found in many products and locations including some candies, toys, and traditional medicines.

The research is based on data from a study - involving more than 1,400 Chinese children - that began in 2004 investigating the influence of lead exposure in relation to the development of children and adolescents' neurocognitive, behavioural and health outcomes.

Using the data from the cohort study, 665 children's blood lead levels were assessed when they were between three and five years old, and sleep was assessed six years later, when the children were between nine and eleven years old.

Child-reported insomnia and use of sleeping pills were two times and three times more prevalent in children with blood lead levels (BLL) greater than or equal to 10 ug/dL (microgram/decilitre) than in children with BLL less than 10 ug/dL.

Lead pollution is pervasive throughout China and other developing countries, and though rates of lead exposure are decreasing due to the phase-out of leaded gasoline and increased public awareness, its persistence presents a significant health risk to children, the researchers said.

The findings will be published in an upcoming issue of the journal Sleep.