Causes of cancer in the world: comparative risk assessment of nine behavioural and environmental risk factors

With respect to reducing mortality, advances in cancer treatment have not been as effective as those for other chronic diseases; effective screening methods are available for only a few cancers. Primary prevention through lifestyle and environmental interventions remains the main way to reduce the burden of cancers. In this report, we estimate mortality from 12 types of cancer attributable to nine risk factors in seven World Bank regions for 2001. We analysed data from the Comparative Risk Assessment project and from new sources to assess exposure to risk factors and relative risk by age, sex, and region. We applied population attributable fractions for individual and multiple risk factors to site-specific cancer mortality from WHO. Of the 7 million deaths from cancer worldwide in 2001, an estimated 2·43 million (35%) were attributable to nine potentially modifiable risk factors. Of these, 0·76 million deaths were in high-income countries and 1·67 million in low-and-middle-income nations. Among low-and-middle-income regions, Europe and Central Asia had the highest proportion (39%) of deaths from cancer attributable to the risk factors studied. 1·6 million of the deaths attributable to these risk factors were in men and 0·83 million in women. Smoking, alcohol use, and low fruit and vegetable intake were the leading risk factors for death from cancer worldwide and in low-and-middle-income countries. In high-income countries, smoking, alcohol use, and overweight and obesity were the most important causes of cancer. Sexual transmission of human papilloma virus is a leading risk factor for cervical cancer in women in low-and-middle-income countries. Reduction of exposure to key behavioural and environmental risk factors would prevent a substantial proportion of deaths from cancer.