Immigrants have lower risk of prostate cancer

[PRESS RELEASE 2008-11-14] Men who have immigrated into Sweden generally run a lower risk of receiving a prostate cancer diagnosis than men born in Sweden, according to a new study from Karolinska Institutet. The researchers conducting the study attribute the variations to environmental and genetic factors and to differences in access to healthcare.

Prostate cancer is the most common form of cancer in men in Sweden and most other Western countries. Incidence rates vary widely, however, between countries and ethnic groups. The reasons for these differences are largely unknown, as are the reasons why the disease develops in the first place.

In order to shed light on the mystery, scientists at Karolinska Institutet have compared incidences of the disease in Swedish-born and foreign-born men. The study covered the years from 1961 to 2004, and was conducted using the national database of migration and health at Karolinska Institute. A total of 3.8 million men, natives and migrants, over the age of 45 and living in Sweden were included in the study.

The results show that immigrant men run, on average, a 40 per cent lower risk of obtaining a cancer diagnosis than men born in Sweden. This lower risk was observed for immigrants from most European countries, with the exception of men born in the Baltic States, whose level of risk was as high as that of the native Swedes. The team also noted that the level of risk amongst immigrant men correlated positively with their length of residency, although this risk was still generally lower than for Swedish-born men.

The scientists believe that part the explanation lies in the fact that relatively many men in Sweden undergo PSA testing, which also reveals cases of non-symptomatic cancer. Such cases would not have been discovered in most other countries.

"Recently arrived foreign-born men might not have as much access to healthcare or knowledge of diagnostic opportunities as men born in Sweden and the Baltic States, which is the group with the longest period of residency in Sweden," says associate professor Tahereh Moradi, who led the study." But this isn't the whole story, as the results also probably reflect genetic differences and differences in environment or lifestyle."

Men born in central Africa or the Caribbean had a tendency to run a higher risk than native Sweden, which corroborates previous studies showing a relatively high risk in men with African origins living in North America and Britain.

"The high risk shown by these groups probably reflects an extant high risk in their countries of origin," says Dr Moradi. "It's unclear what causes this, but there might be a genetic sensitivity in men from these areas."

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