Westernization of Lifestyle and Atherosclerosis in the Japanese: Lessons from the Hawaii – Los Angeles – Hiroshima Study

Japanese Americans include Japanese individuals migrating from Japan to the United States (first-generation Japanese Americans [JA-1]) and their offspring (second- or later-generation Japanese Americans [JA-2]). Although Japanese Americans share their genetic predisposition with the Japanese, their lifestyles have been westernized rapidly and extensively. We conducted a medical survey for atherosclerosis among Japanese Americans living in Hawaii and Los Angeles and native Japanese living in Hiroshima for 50 years since 1970 (the Hawaii–Los Angeles–Hiroshima Study) and obtained the following results: (1) In the 1990s, a westernized lifestyle induced hyperlipidemia among Japanese Americans, and based on the evaluation of the carotid artery intima-media wall thickness (IMT), atherosclerosis was apparently more advanced in Japanese Americans than in native Japanese. In addition, the advancement of atherosclerosis corresponded to the degree of westernization of lifestyles in JA-1 and JA-2. (2) In the 2010s, the serum total cholesterol and low-density lipoprotein cholesterol levels in native Japanese were significantly higher than those in Japanese Americans, and the difference in the progression of carotid artery IMT was smaller between native Japanese and Japanese Americans. (3) Maintaining a healthy Japanese lifestyle since childhood may suppress future worsening of risk factors for atherosclerosis (such as obesity and diabetes mellitus) and contribute to atherosclerosis prevention in the Japanese.