Secondhand smoke the culprit in common cat cancer
A link between a common cancer in household cats and the smoking habits of their owners has researchers concerned and urging further study into a possible connection between non-Hodgkin's lymphoma in humans and second-hand tobacco smoke.
In a study being reported Wednesday in the American Journal of Epidemiology, researchers at the University of Massachusetts at Amherst and Tufts University in Boston found that a cat's risk of developing feline lymphoma, the most common cancer in cats, doubled if it shared a home with a smoker, and increased fourfold if it lived with two smokers. The risk for cats living with a person who smokes a pack of cigarettes or more a day tripled, compared with cats living with non-smokers.
Lead author Elizabeth Bertone, an epidemiologist at the University of Massachusetts, says the finding in cats may signal a similar risk to children.
''Often studying these exposures in pets can tell us about their effects in humans,'' she says. Malignant lymphoma in cats is ''fairly similar in cell type and distribution'' to non-Hodgkin's lymphoma in humans, she says. Both diseases can occur at any age, but incidence tends to peak late in life -- age 10 for cats and about 70 years of age for humans.
Cats, especially those that live indoors all the time, share breathing space with humans, and, like children mouthing toys, may consume smoke particles while grooming their fur.
Passive smoking hasn't been studied in humans with non-Hodgkin's lymphoma, Bertone says, but some studies have found the risk among active smokers is two to three times that of non-smokers, though studies are not consistent.
Non-Hodgkin's lymphoma in humans, like feline lymphoma, is a cancer that starts in lymph tissue and can spread to other organs. The new study suggests that components of tobacco smoke may have a cancerous effect on lymphoid tissue, researchers say.
This is not the first study to link passive smoke and cancer in pets. In 1992 and 1998, John Reif of Colorado State University's College of Veterinary Medicine and Biomedical Sciences reported that dogs that live with smokers have higher rates of both lung and nasal cancers.
''It's a big issue for pet owners,'' Reif says. It may help animal-loving smokers to quit. ''If they're not interested in their own health, maybe they'll do it for their pets.''