Day Care Doesn't Protect Against Asthma
Findings Challenge 'Hygiene Hypothesis'
Sept. 10, 2009 -- Infants and toddlers who attend day care are no less
likely to develop asthma symptoms later in childhood than those who don’t
attend day care, new research finds.
The study challenges the so-called "hygiene hypothesis", which suggests that
early exposure to infections and germs helps protect against asthma and
allergies later in life.
Researchers from Erasmus University in The Netherlands found no evidence for
either a long-term protective or harmful effect associated with day care
attendance in their study involving nearly 4,000 children followed from birth
through age 8.
Children who attended day care did have more viral illnesses with
respiratory symptoms like wheezing in the first years of life and then less
wheezing and steroid use than children who did not attend day care between the
ages of 4 and 8.
But whatever protection day care provided early in childhood disappeared as
the children grew old enough to be diagnosed with asthma, lead researcher Daan
Caudri, MD, tells WebMD.
The study appears in the Sept. 15 issue of the American Journal of
Respiratory and Critical Care Medicine.
“If day care attendance truly was protective, we would expect to see this
protection persist, but that is not what we saw,” he says. “We found no lasting
protective effect against asthma.”
Day Care: No Lasting Impact on Asthma
During the course of the study, parents completed questionnaires designed to
provide detailed histories of their children’s respiratory illnesses and
When they reached the age of 8, most of the children were also assessed for
specific allergies and some also received lung function and airway
hyper-responsiveness evaluations - tests routinely used to diagnose asthma.
Children were classified as early day care attendees if their first
attendance was before the age of 2. These children were found to be twice as
likely as children who did not attend day care to experience wheezing in the
first year of life.
By age 5, however, early day care attendees were less likely to wheeze than
children who had never attended day care, but the difference was not
By the age of 8, there was no difference in asthma-related symptoms like
wheezing in children who had early day care and those who did not.
No difference in wheeze was seen with regard to day care attendance among
boys and girls, but having older brothers or sisters did impact risk.
Children with older siblings who started day care early had more than a
fourfold higher risk of frequent respiratory infections and a more than twofold
risk of wheezing in the first year of life compared to children without older
siblings who did not attend day care.
But even in these high-exposure children, no difference in asthma-related
symptoms was reported by age 8.