In developed countries, the overall cancer mortality is more than twice as high as in developing countries. The main reasons for the greater cancer burden of affluent societies are the earlier onset of the tobacco epidemic, the earlier exposure to occupational carcinogens, and the Western nutrition and lifestyle.
In developing countries, up to 25% of malignancies are caused by infectious agents, including hepatitis B and C virus (liver cancer), human papilloma viruses (cervical cancer), and Helicobacter pylori (stomach cancer). In developed countries, cancers caused by chronic infections only amount approximately 8% of all malignancies.
In North America and some European countries, the overall cancer mortality started to decrease in the 1990s. This is mainly due to the marked decrease in the stomach cancer rate worldwide, to the advances in the early detection and treatment of some major cancer types particular cervical and breast cancer and to a reduction in smoking prevalence.
Tobacco consumption remains the most important avoidable cancer risk. In the 20th century, approximately 100 million people died world-wide from tobacco-associated diseases (cancer, chronic lung disease, cardiovascular disease and stroke). Recent epidemiological studies indicate that the adverse health effects are even greater than previously estimated. Half of regular smokers are killed by the habit. One quarter of smokers will die prematurely during middle age (35 to 69 years).
It has been long recognized that in addition to lung cancer, tobacco smoking causes tumours of the oral cavity, pharynx, larynx, oesophagus, pancreas and bladder. In a recent consensus conference at the International Agency for Research on Cancer in
Contact: Hanna Hanes
Norwegian Cancer Society