Children who experienced violence or bullying may incur DNA damage that leads to premature aging, U.S. researchers said. Lead author Idan Shalev, a postdoctoral researcher at the Duke Institute for Genome Sciences & Policy in Durham, N.C., and colleagues measured cellular aging by studying the ends of children\'s chromosomes -- telomeres -- which act like the plastic tips on shoelaces and prevent the DNA in chromosomes from unraveling, USA Today reported. Previous research has shown several factors could shorten telomeres -- including smoking, radiation and taking care of a chronically ill person. The researchers interviewed the mothers of 236 children at ages 5, 7 and 10. The women indicated whether the children had been exposed to domestic violence between the mother and her partner, physical maltreatment by an adult, or bullying. The researchers measured the children\'s telomeres at ages 5 and 10. The study published in the journal Molecular Psychiatry found the telomeres shortened at a faster rate in children exposed to two or more types of violence, putting them at risk of heart disease 7-10 years earlier than their peers.