New research suggests that very young babies who are with other children are less likely to suffer later from the breathing disease asthma.
Asthma is a disease in which small air passages in the lungs become temporarily blocked.
This causes difficulty breathing.
The disease affects an estimated seventeen-million Americans.
Every year,more than five-thousand people die of asthma in the United States.
It is the most common disease among children.
Day care centers are places where babies and children are cared for while parents are at work.
Researchers studied babies of different ages in day care centers.
They found that babies up to six months old gained the most protection from asthma.
They were only about half as likely to have asthma age thirteen as babies who did not attend day care until later.
Babies who entered day care after the age of six months also received some protection from asthma.
But they did not get as much protection as the younger babies.
Children who entered day care after the age of one showed no increased protection against the disease.
The study also found that children with two or more older brothers or sisters at home also had a lower risk for asthma.
Scientists believe early experiences with bacteria and viruses may help develop a baby's defense system against disease.
Scientists at the University of Arizona College of Medicine did the study.
They studied more than one-thousand children for more than thirteen years.
They also studied the substances in the children's environment that caused breathing problems.
American health officials say asthma cases have increased more than one-hundred percent since Nineteen-Eighty.
Experts say families with fewer children could result in the weakening of a child's defense against disease.
Scientists also say homes cleaned with products that fight bacteria could create the same problem.
The asthma study provides evidence for the idea that keeping a baby in an environment almost free of germs may cause problems later in life.
The study was organized by the National Heart,Lung and Blood Institute.
The results were published recently in the New England Journal of Medicine.