Background The risk of coronary heart disease remains low in Japan, although distributions of several coronary risk factors have become comparable with those in the United States. We prospectively compared coronary atherosclerosis burden, measured with coronary artery calcium (CAC) progression, between men in the 2 countries. Methods In 2 population-based samples of 1712 US White, Black, Hispanic, Chinese men (baseline, 2000-2002) and 697 Japanese men in Japan (2006-2008) aged 45-74 years without clinical cardiovascular disease, we quantified CAC progression by serial computed tomography with medians of 3.4 and 5.2 years between scans, respectively. Results Among White, Black, Hispanic, Chinese, and Japanese men free of baseline CAC, CAC incidence was observed in 35.2%, 26.9%, 29.2%, 18.9%, and 29.2%, respectively. After adjustment for times between scans, demographics, behaviors, coronary risk factors, and their changes between scans, White men had significantly higher CAC incidence than Japanese men (relative risk, 1.68; 95% CI, 1.13-2.50). Among those with detectable baseline CAC, after similar adjustments, all the US race/ethnic groups had significantly greater annual changes in CAC score (mean [95% CI]: 39.4 [35.2-43.6] for White, 26.9 [21.4-32.4] for Black, 30.6 [24.7-36.5] for Hispanic, and 30.2 [22.6-37.8] for Chinese men) than Japanese men (15.9 [10.1-21.8]). Conclusions We found a higher CAC incidence among US White men and greater increases in existing CAC among all the US race/ethnic groups than among Japanese men in Japan. These differences persisted despite adjustment for differences in coronary risk factors.
Keywords: Japan; coronary disease; ethnic groups; humans; risk factors.