The role of medicine in the decline of post-War infant mortality in Japan

The infant mortality rate (IMR) in Japan declined dramatically in the immediate post-War period (1947-60) in Japan. We compared the time trends in Growth Domestic Product (GDP) in Japan against declines in IMR. We then conducted a prefecture-level ecological analysis of the rate of decline in IMR and post-neonatal mortality from 1947 to 1960, focusing on variations in medical resources and public health strategies. IMR in Japan started to decline after World War II, even before the era of rapid economic growth and the introduction of a universal health insurance system in the 1960s. The mortality rates per 1000 infants in 2009 were 2.38 for IMR, 1.17 for neonatal mortality and 1.21 for post-neonatal mortality. The rate of decline in IMR and preventable IMR (PIMR) during the post-War period was strongly correlated with prefectural variations in medical resources (per capita physicians, nurses, and proportion of in-hospital births). The correlation coefficients comparing the number of physicians in 1955 with the declines in IMR and PIMR from 1947 to 1960 were 0.46 [95% confidence interval (CI) 0.19, 0.66] and 0.39 [95% CI 0.11, 0.61], respectively. By contrast, indicators of public health strategies were not associated with IMR decline. The IMR in Japan has been decreasing and seems to be entering a new era characterised by lower neonatal compared with post-neonatal mortality. Furthermore, the post-War history of Japan illustrates that improvement in infant mortality is attributable to the influence of medical care, even in the absence of rapid economic development.