Omega-3 fatty acids and risk of cardiovascular disease in Inuit: First prospective cohort study.

BACKGROUND AND AIMS: No prospective study have ever assessed if marine n-3 polyunsaturated fatty acids protect Inuit against cardiovascular disease as claimed. It is highly relevant as cardiovascular disease (CVD) incidence rates are rising concurrent with a westernization of diet. We aimed to assess the association between blood cell membrane phospholipid content of eicosapentaenoic acid and docosahexaenoic acid (EPA + DHA) on CVD risk in Inuit. METHODS: We used data from a cohort of adult Greenlanders with follow-up in national registers. The main outcome was fatal and non-fatal CVD incidence among participants without previous CVD. The continuous effect of EPA + DHA was calculated as incidence rate ratios (IRRs) using Poisson regression with age as time scale, adjusting for age, sex, genetic admixture, lifestyle and dietary risk factors. RESULTS: Out of 3095 eligible participants, 2924 were included. During a median follow-up of 9.7 years, 216 had their first CVD event (8.3 events/1000 person years). No association between EPA + DHA and CVD risk was seen, with IRR = 0.99 per percentage point EPA + DHA increase (95% CI: 0.95-1.03, p = 0.59). No association was seen with risk of ischemic heart disease (IHD) (IRR = 1.03, 95% CI: 0.97-1.09) and stroke (IRR = 0.98, 95% CI: 0.93-1.03) as separate outcomes or for intake of EPA and DHA. CONCLUSIONS: We can exclude that the CVD risk reduction is larger than 21% for individuals at the 75% EPA + DHA percentile compared to the 25% percentile. We need a larger sample size and/or longer follow-up to detect smaller effects and associations with IHD and/or stroke.

Greenlandic Inuit show genetic signatures of diet and climate adaptation.

The indigenous people of Greenland, the Inuit, have lived for a long time in the extreme conditions of the Arctic, including low annual temperatures, and with a specialized diet rich in protein and fatty acids, particularly omega-3 polyunsaturated fatty acids (PUFAs). A scan of Inuit genomes for signatures of adaptation revealed signals at several loci, with the strongest signal located in a cluster of fatty acid desaturases that determine PUFA levels. The selected alleles are associated with multiple metabolic and anthropometric phenotypes and have large effect sizes for weight and height, with the effect on height replicated in Europeans. By analyzing membrane lipids, we found that the selected alleles modulate fatty acid composition, which may affect the regulation of growth hormones. Thus, the Inuit have genetic and physiological adaptations to a diet rich in PUFAs.

Decrease in vitamin D status in the Greenlandic adult population from 1987-2010.

BACKGROUND: Low vitamin D status may be pronounced in Arctic populations due to limited sun exposure and decreasing intake of traditional food. OBJECTIVE: To investigate serum 25(OH)D3 as a measure of vitamin D status among adult Inuit in Greenland, predictors of low serum 25(OH)D3 concentrations and the trend from 1987 to 2005-2010. DESIGN: A total of 2877 randomly selected Inuit (≥ 18 years) from the Inuit Health in Transition study were included. A sub-sample (n = 330) donated a blood sample in 1987 which allowed assessment of time trends in vitamin D status. RESULTS: The geometric mean serum 25(OH)D3 (25[OH]D2 concentrations were negligible and not reported) in 2005-2010 was lowest among the 18-29 year old individuals (30.7 nmol/L; 95% CI: 29.7; 31.7) and increased with age. In all age-groups it decreased from 1987 to 2005-2010 (32%-58%). Low 25(OH)D3 concentrations (<50 nmol/L) were present in 77% of the 18-29 year old and decreased with age. A characteristic seasonal variation in 25(OH)D3 concentrations was observed (range 33.2-57.1 nmol/L, p<0.001), with the highest concentrations in August to October. Age (2.0% per year increase; CI: 1.7, 2.2), female gender (7.1%; CI: 2.0; 12.5), alcohol intake (0.2% per increase in drinks/week; 0.0; 0.4), and traditional diet (10.0% per 100 g/d increase; CI: 7.9; 12.1) were associated with increased serum 25(OH)D3, whereas smoking (-11.6%; CI: -16.2; -6.9), BMI (-0.6%; CI: -1.1; -0.2) and latitude (-0.7% per degree increase; CI: -1.3; -0.2) were associated with decreased concentrations. CONCLUSION: We identified a remarkable decrease in vitamin D status from 1987 to 2005-2010 and a presently low vitamin D status among Inuit in Greenland. A change away from a traditional diet may well explain the observed decline. The study argues for the need of increased dietary intake of vitamin D and supplementation might be considered.

Exposure to persistent organic pollutants and risk of hypertension among Inuit from Greenland.

BACKGROUND: Exposure to persistent organic pollutants (POPs) is of concern in Arctic populations since these contaminants accumulate in fish and marine mammals, which is an important part of the traditional diet of these populations. Epidemiological and experimental studies have reported significant associations between POPs and increased blood pressure (BP) in populations with different degrees of exposure. OBJECTIVE: We aimed to assess the risk of hypertension related to increasing levels of polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticides. METHODS: Fifteen PCBs and 11 OC pesticides or their metabolites were determined in plasma of 1614 Inuit adults ≥ 18 years living in 9 towns and 13 villages in Greenland. BP was measured using a standardized protocol. The risk of hypertension was estimated through logistic regression using POPs as continuous variables (log-transformed). Hypertension was defined as systolic BP ≥ 140 mm Hg, diastolic BP ≥ 90 mm Hg and/or antihypertensive treatment. RESULTS: Overall, the odd ratios (ORs) of hypertension were not statistically significant for dioxin-like PCBs, non-dioxin-like PCBs and OC pesticides after adjusting for confounders. Once the analyses were stratified by age category (18-39 and ≥ 40 years), increased risk of hypertension was observed for total dioxin-like PCBs among the youngest [OR: 1.34 (95% CI: 1.03-1.74)] while a borderline protective effect was observed for total non-dioxin-like PCBs [OR: 0.81 (95% CI: 0.66-0.99)] among the oldest. Higher risk of hypertension was also associated with increasing p,p'-dichlorodiphenyltrichloroethane (DDT) concentrations among the youngest [OR: 1.42 (95% CI: 1.08-1.85)]. CONCLUSION: Overall, no significant associations were observed between PCBs, OC pesticides and blood pressure in this highly exposed population although the associations differed by age category.

The association between n-3 fatty acids in erythrocyte membranes and insulin resistance: the Inuit Health in Transition Study.

OBJECTIVES: To examine the association between the content of n-3 fatty acids and insulin resistance in an Inuit population. STUDY DESIGN: The Inuit Health in Transition Study was carried out between 2003 and 2007 in Greenland as a cross-sectional study. Our preliminary results are based on the first 452 participants aged 18 and above. Only participants with at least 1 Inuit grandparent and without diabetes were included. METHODS: The contents of n-3 fatty acids and the n-3/n-6 ratio were measured in the erythrocyte membrane phospholipids. BMI was calculated and questions concerning diabetes and ethnicity were answered. Insulin resistance was estimated using the HOMA-IR index based on fasting-glucose and fasting-insulin. RESULTS: We found an inverse association between C20:5 n-3 (EPA), C22:3 n-3, the n-3/n-6 ratio and HOMA-IR and a positive association between C18:3 n-3 cis and HOMA-IR. When adjusted for age, gender, BMI and ethnicity, the association remained statistically significant for C20:5 n-3 (EPA), C22:3 n-3 and C18:3 n-3 cis. CONCLUSIONS: Our findings suggest that some types of n-3 fatty acids may have a protective effect against insulin resistance. The role of potential confounders such as physical activity, diet, energy intake, socio-economic status and contaminants deserves further exploration.

The prevalence of seasonal affective disorder (SAD) in Greenland is related to latitude.

The aim of this study was to determine the prevalence of seasonal affective disorder (SAD) in Greenlanders and Danes living at four different latitudes in Greenland. A Seasonal Pattern Assessment Questionnaire (SPAQ) was mailed to 6021 men and women between the ages of 18 and 59 years living in four different municipalities in Greenland. The recipients were randomly selected from the National Population Register. Approximately 9% of the respondents met the criteria for SAD, and the incidence of SAD varied between a southern municipality and three northern municipalities. The prevalence of SAD was particularly high in northern municipalities. No significant difference was found in the prevalence of SAD between Greenlanders and Danes. The results are comparable with other population studies that have reported a high prevalence of SAD in arctic areas. The clinical implications of our findings and the possibilities for introducing light therapy should be assessed in future studies.

High prevalence of markers of coronary heart disease among Greenland Inuit.

OBJECTIVE: It is a common notion that coronary heart disease (CHD) is rare among the Inuit, possibly due to a high intake of omega-3-fatty acids. The scientific evidence for this is weak and to some extent based on uncertain mortality statistic. The aim of this study was to assess the prevalence of markers of CHD among Greenland Inuit, and to study associations between markers of CHD and behavioral and biological variables. DESIGN: We studied prevalence of angina pectoris (AP), self-reported myocardial infarction (MI), and ECG defined MI and ischaemia in a population survey among 1316 Inuit living in Greenland. Blood tests were supplemented by structured interviews, anthropometry, and measurements of blood pressure, and the participants received an oral glucose tolerance test. RESULTS: The prevalence of symptomatic CHD (AP, self-reported MI) was 7.3% among men and 6.9% among women, and 12.2% and 13.4% of men and women had ischaemic ECG changes. The overall prevalence of CHD (AP+self-reported MI+ECG defined MI) was 10.8% in men and 10.2% in women. The highest prevalence was observed in the least westernized areas in Greenland. Physical inactivity, low education, dyslipidemia, hypertension and diabetes were associated with CHD. CONCLUSION: The prevalence of markers of CHD was not different from that in Western populations. The Inuit is a population undergoing rapid social and health transitions, with the emergence of cardiovascular risk factors, and there is a need for critical rethinking of cardiovascular epidemiology in this population.