Progression of aortic calcification among Japanese in Japan and white and Japanese Americans: a prospective cohort study.

Aims: Continued low mortality from coronary heart disease in Japan, despite deleterious changes in traditional risk factors, remains unexplained. Since aortic calcification (AC) was an early predictor of cardiovascular mortality, we compared the progression and incidence of AC between Japanese in Japan, white Americans, and third-generation Japanese Americans in the ERA JUMP cohort. We examined whether higher blood levels of marine-derived n-3 fatty acids (FAs) in Japanese than in Americans accounted for the difference.

Methods and results: Men (n=700) aged 40-49 years (252 Japanese in Japan, 238 white, and 210 Japanese Americans) were examined at baseline and 4-7 years later. AC was evaluated from the aortic arch to the iliac bifurcation with computed tomography and quantified by the Agatston method. Robust linear regression and linear mixed models were used to compare the progression of AC. Multivariable logistic regression models were fitted to compare the incidence of AC (AC≥50 at follow-up) among those with baseline AC<50. Japanese in Japan had a significantly slower progression of AC than white and Japanese Americans after adjusting for age, baseline AC, follow-up time, and traditional risk factors. White Americans had a significantly higher incidence of AC than Japanese in Japan (OR=4.61 [95%CI, 1.27-16.82]). Additional adjustment for blood levels of n-3 FAs accounted for the difference in AC incidence but not progression.

Conclusion: Japanese in Japan had a significantly slower progression and lower incidence of AC than white Americans. High levels of marine-derived n-3 FAs in Japanese in Japan partly accounted for the difference in incidence.