Updated 28 September 2016

Brain cancer in farmers puzzles scientists

Farmers are known to be at higher risk of a type of brain cancer, but a new study has found no association between types of farming or farm activities and the disease.


Farmers are known to be at higher risk of a type of brain cancer known as glioma, but a comprehensive new study has found no association between types of farming or farm activities and the disease.

"We didn't find a 'culprit' among all the farming activities, the crops, the animals - none of these were associated with a higher risk of glioma," Dr Avima M. Ruder of the National Institute for Occupational Safety and Health in Cincinnati, US, told Reuters Health. "It's something else."

Ruder believes the association is likely due to farmers' well-documented lower risk of having allergies. Studies have found a reduced risk of cancers-including gliomas - among people with allergies, she explained, probably because their "hypersensitive" immune systems are better able to find and destroy abnormal cells before tumours form.

All factors examined

In the current study, she and her colleagues looked at dozens of different factors including pesticide use, type of crops farmed, and length of time living on a farm to determine whether any might account for the increased risk of gliomas found among farmers. They included 288 people with gliomas and 474 healthy controls, all of whom lived on farms in Iowa, Michigan, Minnesota or Wisconsin in the US, at age 18 or afterwards.

People who didn't wash up after applying pesticides or who didn't change clothes after using these chemicals were about three times as likely to develop gliomas, the researchers found. Those who lived on farms where corn, oats, soybeans or hogs were raised were actually at lower risk.

Ruder points out that people who don't follow precautions about pesticide use may be less cautious in other areas of their lives as well; she also noted that gliomas can affect a person's memory, so it's possible that the sick individuals had an impaired recollection of their pesticide use practices.

Whether or not the link between taking these precautions and glioma risk was real, she added, "there are other diseases that you can increase your risk for if you don't follow good work practices. People do get poisoned by pesticides." - (Anne Harding/Reuters Health, June 2009)

SOURCE: American Journal of Epidemiology, June 15, 2009.

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