Narrator: This is Science Today. Although there's a lack of known risk factors for non-Hodgkin's lymphoma, each year it's increasing in both American men and women at a faster rate than all other cancers except melanoma. But a new study is giving researchers more insight into this disease. Epidemiologist Elizabeth Holly of the University of California, San Francisco, found several factors associated with an increased risk.

Holly: Among those were taking ulcer medications - it's probably more likely to be related to the ulcer condition. Also, having had a splenectomy many years prior to the diagnosis of lymphoma was associated with a five-fold increased risk. Also having had polio many years before was associated with nearly a three-fold increased risk.

Narrator: Another risk factor is being overweight.

Holly: In America now with more than half of the population being overweight, this could have an important impact.

Narrator: For Science Today, I'm Larissa Branin.