About four in 10 cancers in the United States are due to lifestyle choices - such as smoking and eating poorly - and other risks that might be avoidable, researchers said on Tuesday. The goal of the study was to calculate "the contribution of several modifiable risk factors to cancer occurrence," said the report in the journal CA: A Cancer Journal for Clinicians.
Factors that are known to raise the risk of cancer included cigarette smoking, exposure to secondhand smoke, excess body weight, drinking alcohol, eating red or processed meat and low fruit and vegetable consumption, said the report.
Others include not getting enough dietary fiber or calcium, lack of exercise, exposure to ultraviolet light and the sexually transmitted infection human papillomavirus (HPV), which can cause cervical and genital cancers as well as tumors in the head and neck region.
Researchers analyzed the prevalence of these known risk factors and the extent to which they increase cancer risk to estimate the proportion of cancers they cause. Then, scientists applied these proportions to current cancer data to estimate the number of associated cases and deaths for 26 cancer types. Of the total 1.57 million cancer cases in the United States in 2014, researchers determined that 42 percent were attributable to these modifiable risk factors.
They found that a similar number of deaths - 45 percent - could be linked to these factors. The top risk was cigarette smoking, which accounted for 19 percent of cancer cases and nearly 29 percent of deaths. Next in line was excess body weight, with 7.8 percent of cases and 6.5 percent of deaths.
Alcohol came in third, responsible for 5.6 percent of cases and four percent of cancer deaths. UV radiation was estimated to cause 4.7 percent of cancers and 1.5 percent of deaths. Physical inactivity was responsible for nearly three percent of cases and 2.2 percent of deaths.