Mortality in East Asian countries in the pre-war period: a quasi-experimental study on healthy immigrant effects.

Life tables of East Asian countries in the prewar period (1926-30) provide a rare quasi-experimental study on immigration. Age and sex-specific mortality of four East Asian countries/regions namely Japan, Korea, Taiwan and Kwanton province of China in the prewar period (1926-30) were drawn from life tables and vital statistics of that time. Mortality curves of these countries/regions were compared to illustrate healthy immigrant effects and racial disposition. Expatriate Japanese men of working age (20-35) had a slightly lower age-specific mortality than indigenous Japanese, suggesting a healthy migrant effect. Also, "humps" in the mortality curves around twenty years of age due to tuberculosis were observed in expatriate Japanese in all three foreign countries/ regions but not in local residents. Mild healthy immigrant effects were observed in expatriate Japanese men of working age. Susceptibility to tuberculosis was attributable to racial disposition rather than to environmental factors.