Cancer in the Sami population of Sweden, 1961-2003 : demographical aspects of different genetic and lifestyle exposure

• Objectives: In previous Nordic studies it has been reported that the overall cancer incidence is lower among the Sami compared to the rest of the population living in the same area. But the relative risk varies among different Sami groups with a lower overall risk among reindeer herders compared to other Sami groups. Diet and lifestyle factors such as physical activity has been suggested to explain these differences together with genetical factors. The objective of this study is to describe the cancer incidence among different Sami groups in Sweden between 1961 and 2003 and to evaluate the effect of demographical changes on risk factors related to Sami lifestyle and heritage. Study Design: Prospective cohort study Methods: The study cohort constitutes of a total of 7 482 reindeer herders and 34 239 non-herders from which subgroups were genealogically defined, carrying with them assumptions of different levels of influence of a traditional Sami life style. Follow up was from 1961 to 2003 and standard incidence ratios (SIR) were calculated using a demographically matched control population as the standard of comparison. Results:Overall lower cancer risk was observed for reindeer herding men compared to the control population while the relative risk for non-herding women was significantly higher. Significantly lower rates of prostate was observed among reindeer herders and higher rates of stomach and ovary was observed among non-herding women. Conclusions: Protective factors in an active, more traditional life style in combination with genertical factors is suggested to explain the lower cancer rates among reindeer herding men. An assumption of declining protective influence of a traditional life style in different Sami groups is supported by an demographical and genealogical analysis of the constitution of different Sami groups. It is indicated that demographical changes resulting in various levels of integration and/or assimilation should be considered when analysing the health status of the Sami.

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