Do Dogs Cause Cancer?- Risk Perception and the Media

19 May 2008

Whilst out for dinner with my parents recently, my mother leaned over the table and slipped me an article that she had cut out of that week’s Sunday paper. The headline read, “Contraceptive coil increases risk of ovarian cancer by 76%”. She then revealed to me that she had used the coil for contraception through the 1980’s (as she had obviously already achieved perfection with her two existing sons) and was concerned that this action had massively increased her risk of cancer. Once I got over the initial horror of discussing my mother’s use of contraception, I went away and looked at the numbers more closely for her.

Ovarian cancer affects around 7000 women each year in the UK and accounts for over 4000 deaths. The lifetime risk of ovarian cancer if you are a woman is about 0.023%, therefore if using the coil increases this risk by 76% then the headline should have read, “Contraceptive coil increases risk of ovarian cancer by 0.017%”, a somewhat less eye-catching headline maybe, but certainly a far less worrying statistic for my mother.

Each week we are bombarded by stories in the media regarding causes and cures for cancer. Probably the most prevalent of these stories regard “super foods”, the foodstuffs lauded to possess Grail like qualities in their prevention of disease. Whilst there are certainly benefits to a healthy varied diet, and some chemicals found in fruit and vegetables may have some protective benefit, these benefits are often greatly exaggerated. Likewise with the foods that are said to increase your risk of cancer. For example several front pages in the UK this year carried the headline “Eating just one sausage a day increases risk of cancer by 20%”. Whilst there certainly appears to be a link between excessive red meat consumption and bowel cancer, the pervading reaction to this article was one of ridicule rather than concern. This reaction is completely understandable; if you search the British popular press for foods that “prevent” cancer and those that “cause” cancer it is remarkable how many make both lists.    

It of course not just foods that are named and shamed in the press but also everyday object ranging from non-stick frying pans to electric blankets to microwaves. Whilst some of these headlines belie some quite interesting science, the way in which they are portrayed often ranges from the misleading to the outlandish. This is probably best exemplified by the Daily Mail headline “Dogs give women breast cancer”, a headline which must have caused blind panic across vast swathes of the pet loving UK. The story states that, “breast cancer patients…were significantly more likely to have kept a dog than a cat. In fact, 79% of all patients had intensive contact with dogs before they were diagnosed.”  However, when you look at the paper this story was taken from it was a study of just 69 patients in one hospital, and the 79% of the patients that had experienced contact with a dog had done so at some point over a 30 year period.

Whilst this is an extreme example, I believe the barrage of these types of frivolous stories around cancer risk are causing the public a great deal of “health message fatigue”, and that this in turn is causing serious problems in the uptake of the health messages that could actually go some way to preventing up to half of all cancer cases. For example, after reading that their dog may be giving them cancer, how many women had a cigarette to steady their nerves?

Dr Ian Lewis- Research Manager, Tenovus