Eldest children and only children were only half as likely to develop non-Hodgkin lymphoma than other people, an Australian researcher said.
People with a history of food allergies also have a 70 per cent lower risk of developing the potentially fatal cancer of the immune cells, University of New South Wales's Associate Professor Andrew Grulich said today.
"The risk of lymphoma is roughly half in first born and only children, compared to later born children," Prof Grulich of the National Centre in HIV Epidemiology and Clinical Research said.
"The fact that it's quite similar in first-born and only children suggests to us that that's related to an exposure very early in life because a first-born child is an only child for the first year of their life until the next child comes along."
Researchers at the UNSW compared 740 people, most of them in their early 60s, who were newly-diagnosed with non-Hodgkin lymphoma with 694 non-sufferers selected at random.
The study also found people with a history of hay fever had a 35 per cent reduced risk of developing non-Hodgkin lymphoma while asthma and eczema sufferers had a slightly reduced risk of developing the cancer.
"It appears that children who are exposed later to infection because they are not exposed to other children have a higher risk of allergy." The cancer had been increasing rapidly over the last 20 to 30 but it was unclear why, he said.
"While it used to be quite a rare cancer, it's now about the sixth most common cause of cancer deaths in Australia," Prof Grulich said. "We don't really have a lot of idea about precisely why this is occurring and we need to know that before we can starting talking about preventive measures."
The findings will be published in the US Journal of the National Cancer Institute. Source: news.com.au