Economic progress as cancer risk factor. II: Why is overall cancer risk higher in more developed countries?

Analysis of data on cancer incidence rates in different countries at different time periods revealed positive association between overall cancer risk and economic progress. Typical explanations of this phenomenon involve improved cancer diagnostics and elevated exposure to carcinogens in industrial countries. Here we provide evidence from human and experimental animal studies suggesting that some other factors associated with high economic development and Western life style may primarily increase the proportion of susceptible to cancer individuals in a population and thus contribute to elevated cancer risks in industrial countries. These factors include (but not limited to): (i) better medical and living conditions that "relax" environmental selection and increase share of individuals prone to chronic inflammation; (ii) several medicines and foods that are not carcinogenic themselves but affect the metabolism of established carcinogens; (iii) nutrition enriched with growth factors; (iv) delayed childbirth. The latter two factors may favor an increase in both cancer incidence rate and longevity in a population. This implies the presence of a trade-off between cancer and aging: factors that postpone aging may simultaneously enhance organism's susceptibility to several cancers. Key words: cancer risk, individual susceptibility, economic progress, agin