STOCKHOLM - Lifestyle during the first 20 years of life is a more important factor than original nationality when defining the risk of cancer, Swedish studies of immigrants show.
The survey of some 600,000 immigrants, who came to Sweden in their 20s and became parents there, showed that their cancer risks
were in line with those of their native countries.
But their Swedish-born children had a similar cancer incidence to native Swedes, another study of some 600,000 immigrants, mainly from Europe and North America, showed.
"Internationally, there are clear differences between cancer risks," said Professor Kari Hemminki of the Karolinska Institute university hospital.
"But these differences disappear within one generation, so environment must clearly be a significant cancer factor."
As the first 20 years of a person's life were so important in defining the risk of cancer, preventive measures should target that period, he said.
In some types of cancer it was clear why the risks were different between people who spent their first 20 years outside Sweden and their children.
For example, the risk of lung cancer decreased among the immigrants' children because Swedes tended to smoke less.
The higher risk of stomach cancer among immigrants compared with their children and native Swedes could be linked to eating habits, vitamin deficiencies and use of salt - all factors linked to this type of cancer, said Professor Hemminki.
Darker-skinned children of immigrants were as prone to skin cancer as blond Swedes, and much more so than their own parents, due to a similar sunbathing style among youths regardless of origin.
The studies were carried out using the Swedish Family Cancer Database, which has information on all people born in Sweden after 1931 and their parents. The International Journal of Cancer will publish the findings on May 10.
- REUTERS
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