The prevalence of aortic calcification in Japanese compared to white and Japanese-American middle-aged men is confounded by the amount of cigarette smoking

Background: The prevalence of coronary artery calcification (CAC) in Japanese men is lower than in white and Japanese-American men. It is unclear if aortic calcification (AC) strongly linked to smoking is also lower in Japanese men who have many times higher smoking prevalence compared to US men. Methods: We conducted a population-based study of 903 randomly-selected men aged 40-49 years: 310 Japanese men in Kusatsu, Japan, 301 white men in Allegheny County, US, and 292 Japanese men in Hawaii, US (2002-2006). The presence of AC was assessed by electron-beam tomography. AC was defined as Agatston aortic calcium scores (AoCaS) > 0 and ≥ 100. Results: Japanese (35.8%) had significantly less AoCaS > 0 compared to both white (68.8%, p < 0.001) and Japanese-American (62.3%, p < 0.001) but similar AoCaS ≥ 100 (19.4%, 18.3%, 22.6%, respectively, p = 0.392). The pack-years of smoking, which was highest in Japanese, was the most important single associate of AC in all populations. Additionally age, low-density-lipoprotein cholesterol (LDL-C), and triglycerides in Japanese; body-mass index (BMI) in white; and BMI, LDL-C, hypertension, diabetes, and lipid medications in Japanese-American were independent associates of AC. The risk of AC using either cut points adjusted for pack-years of smoking and additional risk factors was lower in Japanese compared to both white and Japanese-American. AC and CAC had moderately positive and significant correlations in Japanese (r = 0.26), white (r = 0.39), and Japanese-American (r = 0.45). Conclusions: The prevalence of AC defined both > 0 and ≥ 100 was significantly lower in Japanese than in white and Japanese-American men after adjusting for cigarette smoking and additional risk factors.