The Metabolic Syndrome in Inuit

Inuit have been considered to have a lower prevalence of diabetes and age-adjusted mortality from cardiovascular disease than the general population (1,2). This observation has prompted investigation of both traditional and newer cardiovascular risk factors. A new risk cluster called the metabolic syndrome, defined as three or more of 1) fasting glucose ≥6.1 mmol/l; 2) blood pressure ≥130/85 mmHg; 3) triglycerides ≥1.69 mmol/l; 4) HDL cholesterol <1.04 mmol/l in men or <1.29 in women; and 5) waist circumference >102 cm in men or >88 cm in women (3), has not been evaluated in the Inuit. We thus determined the prevalence of the metabolic syndrome among 168 Inuit (48.2% women) and 53 Caucasian control subjects (38.5% women) who were residents in the arctic and had participated in a cardiovascular survey in 1989–1991 (2). Using the 2001 criteria, we found that Inuit had a lower prevalence of the metabolic syndrome (13.1%) compared with both regional Caucasian control subjects (20.8%) and Caucasian subjects from the contemporaneous 1988–1994 National Health and Nutrition Examination Survey (NHANES) III (4) (23.8%, P = 0.0013). We next examined each of the metabolic syndrome components in Inuit and resident Caucasian control subjects. The frequencies of hypertriglyceridemia (7.1 vs. 24.5%, P = 0.0005) and of depressed HDL cholesterol (20.8 vs. 47.1%, P = 0.0002) were significantly lower in Inuit than in Caucasians. In contrast, the frequencies of high blood pressure (11.9 vs. 9.4%, P = NS), elevated fasting serum glucose (53.6 vs. 60.4%, P = NS), and increased waist circumference (28.6 vs. 18.9%, P = NS) were not different between Inuit and Caucasians. Furthermore, 32.1% of Inuit, compared with only 13.2% of Caucasians, were free of any positive metabolic syndrome variable (P = 0.0072).

Thus, Inuit studied in 1989–1991 had a lower prevalence of the metabolic syndrome compared with two independent Caucasian samples studied at the same time. Inuit had a favorable lipid profile, specifically lower triglycerides and higher HDL cholesterol, despite a trend to increased prevalence of higher waist circumference. Although genetic factors might have played a role, lower plasma triglycerides and higher plasma HDL cholesterol are both related to lifestyle factors, mainly activity level and diet. In this regard, it may be important that the consumption of marine-based fats by the Inuit study participants in 1989–1991 was high (2). Therefore, Inuit had a lower prevalence of the metabolic syndrome compared with Caucasians, which is consistent with the previous impression of lower cardiovascular disease and diabetes prevalence. Because lifestyle is changing dramatically in this “population in transition” (5), systematic reevaluation of the metabolic syndrome would be important in order to identify interval changes that could predict future increases in diabetes and cardiovascular disease (6).