Comparison of carotid plaque burden among healthy middle-aged men living in the US, Japan, and South Korea

Highlights

• White men in the US have four-fold higher carotid plaque than Japanese and twice as much as Koreans.

• These differences persist after accounting for lower BMI among east Asians in the study.

• Overall, age, hypertension and diabetes status are associated with higher carotid plaque burden.

Abstract

Background

Carotid plaque has emerged as a marker of coronary heart disease (CHD) risk. Comparison of carotid plaque burden between different race/ethnic groups may provide a relative estimate of their future CHD risk.

Methods

We conducted a population-based study among apparently healthy middle-aged men aged 40–49 years (ERA JUMP study (n = 924)) and recruited 310 Whites in Pittsburgh, US, 313 Japanese in Otsu, Japan, and 301 Koreans in Ansan, South Korea. The number of carotid plaque and CHD risk factors was assessed using a standardized protocol across all centers. The burden of carotid plaque was compared between race/ethnic groups after adjustment for age and BMI, and after multivariable adjustment for other CHD risk factors using marginalized zero-inflated Poisson regression models. Cross-sectional associations of risk factors with plaque were examined.

Results

Whites (22.8%) had more than four-fold higher prevalence (p < 0.01) of carotid plaque than Japanese men (4.8%) while the prevalence among Koreans was 10.6%. These differences remained significant after adjustment for age, BMI as well as other risk factors – incidence density ratio (95% confidence interval) for plaque was 0.13 (0.07, 0.24) for Japanese and 0.32 (0.18, 0.58) for Koreans as compared to Whites. Age, hypertension and diabetes were the only risk factors significantly associated with presence of carotid plaque in the overall population.

Conclusion

Whites have significantly higher carotid plaque burden than men in Japan and Korea. Lower carotid plaque burden among Japanese and Koreans is independent of traditional CVD risk factors.

Introduction

Presence of plaque in the carotid artery has emerged as a strong predictor of coronary heart disease (CHD) [1]. Carotid plaque is recently reported to be a stronger predictor of CHD than carotid intima-media thickness (IMT) [1,2] which is commonly used as a surrogate measure of subclinical atherosclerosis in epidemiological studies. Thus, comparison of carotid plaque burden between different race/ethnic groups may provide a relative estimate of their future risk of CHD.

CHD remains the leading cause of mortality in the United States (US), with more than three-fold higher CHD mortality rates in the US than in Japan [3]. Although being industrialized for several decades with westernization of diet and lifestyle, Japan continues to have extremely low CHD rates. Similar to Japan, South Korea has extremely low CHD rates in spite of rapid westernization [3]. While several studies have examined racial/ethnic differences in CHD as well as markers of subclinical disease such as carotid IMT [4,5], only a few studies have compared prevalence of carotid plaque across different race/ethnic groups [6]. Further, previous studies have used varying methodology to examine and define carotid plaque [1], thus limiting the validity of any post-hoc comparison of plaque prevalence between different studies. With the emergence of carotid plaque as a predictor of CHD, it is now important to systematically examine the differences in carotid plaque burden between populations in the US and Japan.

Although many population-based studies have assessed the prevalence of carotid plaque [6,7], no study has compared the burden of carotid plaque between the US and Japan or South Korea. We used a standardized protocol to compare the number of carotid plaques among Whites in the US, Japanese in Japan, and Koreans in South Korea in the ERA JUMP study, an international population-based study for assessing subclinical atherosclerosis in 40–49 year-old men. We have previously reported lower coronary atherosclerosis and lower IMT among Japanese men than US whites [8]. Therefore, we hypothesized that the burden of carotid plaque is highest among Whites. We further examined which CHD risk factors were associated with the presence of carotid plaque in this sample population.