A study has found that children with TV sets in their room sleep less than those who do not. 
The study was conducted by the Massachusetts General Hospital for Children and the Harvard School of Public Health. 
The research was carried out on 1,800 children between the ages of six months and 8 years. 
It found that for every hour of television a child watches, they lose approximately seven minutes of sleep. 
The study also found that children who had a TV set in their bedroom got a full half an hour less sleep than children who do not have a TV in their bedroom. 
It also found that boys were more affected by having a TV in the bedroom. 
The reserach was carried out as part of Project Viva - a long -term project that studies the effect of various aspects on mothers and children from birth.