Sami lifestyle and health : epidemiological studies from northern Sweden

Sammanfattning: The aim of this PhD thesis was to expand the current knowledge of “traditional Sami” diet and lifestyle, and to test aspects of the Sami diet and lifestyle, specifically dietary pattern, macronutrient distribution and coffee consumption, in population-based epidemiological studies of mortality and incident cardiovascular disease and cancer in a general population.In Paper I, semi-structured interviews were conducted with 20 elderly Sami concerning their parent’s lifestyle and diet 50-70 years ago. Questionnaire data from 397 Sami and 1842 matched non-Sami were also analyzed, using non-parametric tests and partial least square methodology.  In Papers II-IV, mortality data and incident cancer data for participants in the Västerbotten Intervention Program (VIP) cohort were used for calculations of hazard ratios by Cox regression. In Paper II, a Sami diet score (0-8 points) was constructed by adding one point for each intake above the median for red meat, fatty fish, total fat, berries and boiled coffee, and one point for each intake below the median for vegetables, bread and fibre. In Paper III, deciles of energy-adjusted carbohydrate (descending) and protein (ascending) intake were added to create a Low-Carbohydrate, High-Protein (LCHP) score (2-20 points). In Paper IV, filtered and boiled coffee consumption was studied in relation to incident cancer. In Paper V, a nested case-control study of filtered and boiled coffee consumption and acute myocardial infarction, risk estimates were calculated by conditional logistic regression.Surprisingly, fatty fish may have been more important than reindeer meat for the Sami of southern Lapland in the 1930’s to 1950’s, and it is still consumed more frequently by reindeer-herding Sami than other Sami and non-Sami. Other dietary characteristics of the Sami 50-70 years ago and present-day reindeer-herding Sami were high intakes of fat, blood, and boiled coffee, and low intakes of bread, fibre and cultivated vegetables (Paper I). Stronger adherence to a “traditional Sami” diet, i.e. a higher Sami diet score, was associated with a weak increase in all-cause mortality, particulary apparent in men (Paper II). A diet relatively low in carbohydrates and high in protein, i.e. a high LCHP score, did not predict all-cause mortality compared with low LCHP score, after accounting for saturated fat intake and established risk factors (Paper III).  Neither filtered nor boiled coffee consumption was associated with cancer for all cancer sites combined, or for prostate or colorectal cancer. For breast cancer, consumption of boiled coffee ≥4 versus <1 occasions/day was associated with a reduced risk. An increased risk of premenopausal and a reduced risk of postmenopausal breast cancer were found for both total and filtered coffee. Boiled coffee was positively associated with the risk of respiratory tract cancer, a finding limited to men (Paper IV). A positive association was found between consumption of filtered coffee and the risk of acute myocardial infarction in men (Paper V).In conclusion, the findings of Paper I, in particular the relative importance of fatty fish compared to reindeer meat in the “traditional Sami” diet of the 1930’s-1950’s, suggest that aspects of cultural importance may not always be of most objective importance. The findings of Papers II-V generally did not support health benefits for the factors studied. The relatively good health status of the Sami population is therefore probably not attributable to the studied aspects of the “traditional Sami” lifestyle, but further investigation of cohorts with more detailed information on dietary and lifestyle items relevant for “traditional Sami” culture is warranted.