Population-based study of high plasma C-reactive protein concentrations among the Inuit of Nunavik

Abstract

Background: The shift away from traditional lifestyle in the Inuit population over the past few decades has been associated with an increased prevalence of coronary heart disease (CHD) risk factors such as obesity, high blood pressure (BP) and diabetes. However, the impact of this transition on the pro-inflammatory marker high-sensitivity C-reactive protein (hs-CRP) has not been documented.

Objectives: To examine the prevalence of elevated plasma hs-CRP concentrations in Inuit from Nunavik in the province of Quebec (Canada) and identify anthropometric, biochemical and lifestyle risk factors associated with elevated hs-CRP.

Design: A population-representative sample of 801 Inuit residents from 14 villages of Nunavik, aged between 18 and 74 years, was included in the analyses. Subjects participated in a clinical session and completed questionnaires on lifestyle. Multivariate logistic regression was used to determine risk factors for elevated hs-CRP.

Results: Elevated plasma hs-CRP concentrations (≥ 2 mg/L) were present in 32.7% (95% confidence interval (CI) 29.5-35.8) of the Inuit adult population and were more prevalent among women than among men (36.7% vs. 29.0%, p=0.007). Multivariate logistic regression analysis indicated that every 1 mmHg increase in systolic BP was associated with a 3% increase in the odds of having hs-CRP concentrations ≥ 2 mg/L in the Inuit population (95% CI 1.01-1.04). The combination of older age (≥ 50 vs. <30 years) and elevated waist circumference (gender-specific cut-off values) in a multivariate logistic model was also associated with a 13.3-fold increase in the odds of having plasma hs-CRP concentrations ≥ 2 mg/L (95% CI 5.8-30.9).

Conclusions: These data indicate that elevated hs-CRP is relatively prevalent among Inuit with values that are similar to those seen in Canadian Caucasian populations. Sex, age, waist circumference and systolic BP are major factors that increase the risk of this inflammatory phenotype among Inuit from Nunavik, despite their different lifestyle background compared with Caucasians.

Keywords: C-reactive protein; Inuit; Nunavik; aging; prevalence; risk factors; sex; systolic blood pressure; waist circumference.

Fig. 1

Flow of participants through the Nunavik Inuit Health Survey 2004. *58 subjects were excluded because they had hs-CRP concentrations ≥10 mg/L, which is indicative of an acute inflammatory response (17).

Fig. 2

Population prevalence of elevated hs-CRP concentrations among Inuit from Nunavik. Note: hs-CRP = high-sensitivity C-reactive protein; MetS = metabolic syndrome. Population prevalence of elevated hs-CRP concentrations (≥2.0 mg/L) is presented according to sex (A), age (B), waist circumference (C) and the presence of MetS (D). p-Values for between-groups differences in frequencies were obtained using the Chi-square test. Values within parentheses are 95% confidence intervals. Prevalence values are unadjusted for other variables. In panels C and D, high waist circumference cut-offs (≥90 cm in men and ≥80 cm in women) and MetS criteria are those suggested by the International Diabetes Federation (11).

Fig. 3

Odds ratio (OR) for elevated high-sensitivity C-reactive protein (hs-CRP) concentrations according to the combined impact of age and waist circumference. Note: A significant age*waist circumference multiplicative interaction (p interaction = 0.04) was found on the odds of having elevated hs-CRP concentrations (≥2.0 mg/L) among the Nunavik Inuit population, using a multivariate logistic regression model. To illustrate the interaction, 6 groups were created based on the combination of different strata of age (<30, 30–49, ≥50 years) and waist circumference (low/high) and were simultaneously entered into a logistic model, with the combination of age <30 years and low waist circumference as the reference group (OR = 1). OR and 95% confidence intervals (in parentheses) were obtained for each group and are adjusted for high-density lipoprotein cholesterol, triacylglycerol (log transformed), insulin (log transformed), systolic blood pressure (BP), diastolic BP, sex and smoking. Positive associations of female sex and systolic BP with elevated hs-CRP concentrations remained significant in this model (p ≤ 0.01). High waist circumference cut-offs were ≥90 cm in men and ≥80 cm in women, as suggested by the International Diabetes Federation (11). *OR significantly higher than the reference group, p ≤ 0.0003.