Nearly half of cancer deaths in U.S. blamed on unhealthy behaviour

A new look at cancer in the U.S. finds that nearly half of cancer deaths are caused by smoking, poor diet and other unhealthy behaviours.

That’s less than commonly-cited estimates from more than 35 years ago, a result of new research methods and changes in American society. Smoking rates have plummeted, for example, while obesity rates have risen dramatically.

The study found that 45 per cent of cancer deaths and 42 per cent of diagnosed cancer cases could be attributed to what the authors call “modifiable” risk factors. These are risks that are not inherited, and mostly the result of behaviour that can be changed, like exposure to sun, not eating enough fruits and vegetables, drinking alcohol and, most importantly, smoking.

A British study conducted in 1981 attributed more than two-thirds of cancer deaths to these factors.

The study used 2014 data and was conducted by the American Cancer Society. It was published online Tuesday in CA: A Cancer Journal for Clinicians.

“We thought it was time to redo those estimates,” said Dr. Otis Brawley, the cancer society’s chief medical officer and one of the study’s authors.

Smoking was the leading risk by far, accounting for 29 per cent of deaths. Excess body weight was next at 6.5 per cent, and alcohol consumption was third at 4 per cent.

The authors ran separate calculations for different types of cancer by age group and gender to try to account for how risk factors affect different groups of people, then added them together to understand the national picture.