Asthmatics and hay fever sufferers get a surprise benefit from
their condition, according to research suggesting they have some
protection from cancer of the lymph system.
The study by University of NSW researchers shows that people with
one allergic condition are up to 25% less likely to get the most
common type of Non-Hodgkin Lymphoma (NHL).
And the more sneezing or wheezing ailments they have the better, it
seems.
Those suffering three such conditions were judged to have a 40%
reduced risk and sufferers who have had asthma and hay fever for a
long time appeared to be most protected.
Lead researcher Dr Claire Vajdic said the surprise results, to be
presented at a medical conference in Sydney next week, were
contrary to expectations.
She said the only known strong risk factors for NHL were immune
deficiency and certain infections.
These occur in people with uncontrolled HIV infection, and those
who have had a solid organ transplant.
"So we thought other forms of immune dysregulation such as atopic
diseases - including hay fever, asthma and food allergies - might
relate to the development of lymphoma," she said.
"It was therefore intuitive to think that these conditions would
increase the risk, but in fact, they do the reverse."
The results are being heralded as significant given the incidence
of NHL in developed countries has escalated dramatically in the
past 50 years.
It is three times more prevalent now than it was in 1950, making it
the sixth most common cause of cancer death in Australia, yet the
cause of most cases remains unknown.
The research found that risk was reduced only in the most common
type of the cancer, called B-cell NHL.
"While the relevant biological mechanisms are not yet known, the
pooled data indicate that chronic and multiple atopic conditions
impart the greatest reduction in risk," Dr Vajdic said.
"Investigation of the genetic and environmental factors underlying
atopy and the apparent inverse effect of atopy on NHL risk will
inform our understanding of the complex biological pathways that
may be involved."
The review, funded by the Leukaemia Foundation, was a pooled
analysis of data from 13 studies involving about 13,500 NHL cases
and 16,500 control participants.
