Day Care, Play Groups Cut Leukemia Risk?
Study: Social Contact May Cut Kids' Risk of Developing Leukemia
April 29, 2008 -- Children who attend day
care or play groups may be less likely to develop leukemia.
So says Patricia Buffler, PhD, of the University of California at Berkeley.
She and her colleagues reviewed 14 studies on leukemia and kids' social
contacts with other children, including at day care and in play groups.
Together, the studies included about 6,100 kids with leukemia and 13,700
children without leukemia. The kids' parents answered questions about the
children's social exposure to other kids.
"We calculated an overall estimate of effect, which suggests that the
reduction in risk may be as high as 30% [and] with the better studies as high
as 40%," Buffler tells WebMD.
These findings show that "early social contacts, as estimated from
day care and other settings, appear to be consistently and significantly with a
decreased risk of childhood leukemia," says Buffler, who presented the
findings today in London at the Causes and Prevention of Childhood Leukemia
"More research needs to be done to establish this, but it's been
proposed that the earlier the child is exposed to a variety of infectious
agents, the better the immune system is primed," Buffler explains. Exposure
to other kids at day care and in play groups provides opportunity for common
childhood infections, which may help the immune system respond more
effectively, according to this theory.
"I think the earlier the child is exposed, the better," Buffler
says. "The peak age for acute lymphoblastic leukemia [the most common type
of leukemia in young children] is 2-5 years of age, so the exposures of
interest would take place prior to that."
The pattern Buffler's team noted wasn't just about day care. "We looked
at all types of social contact, not just day care, and all types of social
contact were found to be protective," says Buffler. She adds that the
pattern was weaker for kids with many siblings because by being around their
brothers and sisters, those kids had plenty of contact with other children even
if they didn't go to day care.
There are three things to keep in mind about Buffler's review.
First, the reviewed studies were observational, so they don't prove that
social contacts prevent childhood leukemia. "These types of studies can
only point to or provide clues about what might be involved -- in this
instance, infection and a disregulated immune system," says Buffler.
Second, the theory about infection and leukemia risk hasn't been proven. The
reviewers can't promise that social contact prevents childhood leukemia, and
they're not blaming childhood leukemia on insufficient social contact.
Third, leukemia is rare among kids. It occurs in about one of every 29,000
U.S. children per year, according to the National Cancer Institute. Though a
30% or 40% drop in the relative risk of leukemia may sound large, the overall
risk of developing leukemia is still low.
Still, "the epidemiological data are fairly consistent and hopefully
will stimulate more research on what mechanisms might be involved," says