Variations in the birth-season effects on height attainment in the two Koreas
Abstract
Background : Previous studies have reported a consistent link between birth season and height in northern and southern hemisphere humans, creating a pattern in which spring birth cohorts are the tallest, and autumn birth cohorts are the shortest. Aim : A previous study on heights of children born during the North Korean famine of the 1990s revealed a pattern inconsistent with other studies, suggesting that adverse living conditions during the famine may have caused the atypical result. This paper investigates this issue by comparing the anomalous finding to other Korean data. Subjects and methods : The present study investigated birth season–height patterns in South Koreans and North Koreans born during the famine as well as in pre- and post-famine periods, and Colonial Koreans raised prior to the political separation of the Korean peninsula by making use of height error bars classified by birth season. The study was limited to the Korean peninsula, thus genetic factors are unlikely to have had an impact on the results. Results : With the exception of North Koreans born during the famine, all groups followed the same birth season–height pattern, a pattern consistent with other globally reported patterns. This suggests that adverse conditions during the famine are likely factors resulting in the anomalous birth season–height pattern in North Koreans born during the famine. Conclusion : Birth season–height patterns of Koreans follow the typical global pattern, but extreme environmental circumstances during the North Korean food crisis appear to have significantly disrupted that pattern.