Brain tumour

People with at least three years of higher
education are at greater risk for cancerous
brain tumours than those with no more than

nine years of schooling, perplexed
researchers said Tuesday.
"There is a 19 percent increased risk that
university-educated men could be diagnosed
with glioma," said Amal Khanolkar, a
scientist at the Institute of Child Health in
London and lead author of a study in the
Journal of Epidemiology and Community.
For women, he said, the risk rose by 23
percent.
"It was a surprising result which is difficult
to explain," Khanolkar told AFP.
Concretely, the increase in risk is minimal
because such brain tumours are rare.
At the lowest level of education, the
chances of glioma were reported at five in
3,000. At the other end of the educational
spectrum, the odds increased to six in
3,000.
But the question remained as to whether
the gap -- no matter how small -- was real
and, if so, what caused it.
Earlier research exploring a possible link
between education or social level, on the
one hand, and the frequency of brain
tumours, on the other, had been
inconclusive.
To "put to rest" these conflicting findings,
Khanolkar and colleagues at the Karolinska
Institute medical university in Stockholm
used a new approach.
Rather than comparing a small number of
brain tumour patients with healthy
individuals, they sifted through the health
records of 4.3 million adults tracked by the
Swedish public health system from 1993 to
2011.
The researchers distinguished between
three kinds of brain tumours -- two of them
non-cancerous -- with different causes.
The strong link between education level and
tumour incidence held for all three types,
but was strongest for deadly gliomas.
Interestingly, an even higher risk gap was
found between low-income manual labourers
and high-income men and women who did
not work with their hands.
- Why? -
Gliomas are malignant brain tumours which
grow rapidly and cause severe symptoms,
including migraines, nausea and memory
loss.
The survival rate is very low.
The study did not seek to explain the link
between higher education and tumours, nor
did it consider the potential impact of
environmental and lifestyle factors, such as
smoking or alcohol consumption.
The most common explanation for risk levels
that rise with years spent in the classroom
is that people with a higher education or
income "have a better awareness of
symptoms," Khanolkar said.
This would mean they are more likely to
seek help and receive a correct diagnosis.
But while this may be true in a country with
a health system that clearly favours the
well-to-do, the argument is far less
convincing in the Swedish context, the
researchers said.
"Sweden has a universal, tax-based health
care system," said Khanolkar. Everybody has
roughly the same access to treatment.
Moreover, he added, gliomas form very
rapidly -- often within 48 hours -- and are
excruciatingly painful.
"The symptoms are not avoidable -- you
can't sit at home and not seek care," he
said.
To further their probe, the team will canvass
an updated version of the database for
possible correlations between ethnicity and
brain tumour risk.
Underlying genetic variation in populations
from different geographic regions -- where
certain mutations are more or less common
-- could be a factor, Khanolkar
acknowledged.
One expert, commenting on the study,
pointed to other possible culprits.
"Two additional factors which might be of
interest in this context are height and, in
women, hormone replacement therapy," said
James Green, a clinical epidemiologist at
the University of Oxford.
Risk of brain tumours -- as of most cancers
-- is higher in taller people, and taller people
tend to be richer and more educated," he
noted.
"Hormone replacement therapy increases
risk of brain tumours, and its use tends to
vary by socio-economic group."