Birth Month May Influence
Brain Cancer Risk
The time of year in which a person is
born may somehow sway the risk of developing brain cancer in adulthood,
new research suggests.
If confirmed by further studies,
the findings would indicate that some as yet unknown factors before
or soon after birth contribute to brain cancer development decades
later, according to the authors.
Their study of brain cancer patients
and cancer-free adults the same age found that the risk of developing
the disease appeared highest for people born in January or February
and lowest for those born in July or August.
And for reasons that are unclear,
the association between birth season and cancer risk was most
pronounced among people who were left-handed or ambidextrous --
with those born in the late fall through early spring having a
However, the researchers stress
that left-handed winter babies should not find the study results
alarming. For one, it's possible that the associations were simply
due to chance, lead author Dr. Alina V. Brenner of the National
Cancer Institute, Bethesda, Maryland, told Reuters Health.
The aim of the study, the researcher
explained, was to unearth possible new clues about the causes
of brain tumors -- something that scientists currently know little
If the association between birth
season and brain cancer risk is real, then researchers could investigate
the factors that operate during pregnancy and early infancy and
vary by season. Some "candidate" factors, according to Brenner
and her colleagues, include infections, maternal diet, environmental
toxins and hormonal influences during pregnancy.
But, Brenner noted, too little
is known to tell which, if any, of these factors could be at work.
It is also unclear what the crucial point in pregnancy might be.
The study, published in the journal
Neurology, included 686 brain cancer patients from three U.S.
hospitals and 799 "control" patients hospitalized for non-cancerous
conditions. It is one of a number of studies that have tied disease
risk to birth season.
For example, an "excess" of winter
births has been found among children with brain cancer, and among
people with conditions such as epilepsy, schizophrenia and bipolar
disorder. Overall, birth season has been most strongly tied to
diseases affecting the central nervous system, which is vulnerable
to environmental insults during development.
As for why the association between
birth season and brain cancer was stronger among lefties and ambidextrous
people, there is no clear reason, according to the researchers.
They included handedness in their analysis, in part, because handedness
is thought to be influenced by prenatal and early-life factors
that affect the central nervous system.
In addition, the researchers had,
in a previous study, found evidence of a lower risk of brain cancer
among left-handed people. Why those born in the winter might have
a greater risk than their warmer-month peers is unknown.
SOURCE: Neurology, July 27, 2004.
Reference Source 89
August 16, 2004