Worse cardiometabolic health in African immigrant men than African American men: reconsideration of the healthy immigrant effect

Abstract

Background: The healthy immigrant effect is a phrase that has been used for decades to describe better cardiometabolic health in African immigrants than African Americans. The recent global increase in cardiometabolic diseases raises the possibility that immigrant health may be changing. Therefore, a new assessment of cardiometabolic health in African immigrants is warranted.

Methods: Glucose tolerance status, blood pressure, and visceral adipose tissue (VAT) volume were compared in 214 self-identified healthy men comprised of 138 African immigrants, 76 African Americans, mean age 36±9 years [mean±standard deviation (SD); range 20-64 years]. Insulin resistance was defined by the lowest quartile of the insulin sensitivity index (SI≤2.28 mU/L(-1)·min(-1)). The waist circumference (WC) which predicts insulin resistance was determined using receiver operating characteristic curves and the Youden index.

Results: Body mass index (BMI) and WC were lower in African immigrants than African Americans (BMI, 27.4±3.8 vs. 29.3±5.5 kg/m(2), P<0.01; WC, 91±11 vs. 97±16 cm, P<0.01). However, blood pressure, fasting glucose, and 2-hr glucose were higher in the African immigrants (all P<0.01). In addition, African immigrants had a higher prevalence of previously undiagnosed diabetes (8% vs. 0%, P<0.01) and prediabetes (35% vs. 22%, P<0.01). After adjusting for WC, African immigrants had more visceral adipose tissue (VAT) than African Americans (P<0.01). Consequently, the WC that predicted insulin resistance was 92 cm in African immigrants but 102 cm in African Americans.

Conclusion: African immigrants were less obese than African Americans but had worse cardiometabolic health, specifically higher glucose levels, more hypertension, and greater visceral adiposity. Overall, the healthy immigrant effect may no longer be valid.

FIG. 1.

Central body fat distribution. (A) Correlation between visceral adipose tissue (VAT) and waist circumference. (B) Subcutaneous adipose tissue (SAT) and waist circumference. African immigrants are represented by open circles (◯) and the solid regression line; African Americans are represented by solid circles (●) and a dashed regression line. Pearson correlation coefficients are provided.

FIG. 2.

Waist circumference of risk predictions. Area under the receiver operating characteristic (AUC-ROC) curve for the ability of waist circumference (WC) to predict insulin resistance is shown. Optimal WC calculated by the Youden index is provided. (A) African immigrants; (B) African Americans.