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This investigation partially confirmed the existence of the relative age effect in wrestlers of Sumo, a traditional sport in Japan. In 1960, 1980, 2002 and 2010 Sumo wrestlers of upper classes from yokozuna to makushita were analyzed for relative age effect. Chi-square test (X^2) and spearman rank-order correlation (rs) were calculated as test statistics. The results were followed; 1960 : X^2_{(3)}=1.620p=.655, rs=-.126p=.697 1980 : X^2_{(3)}=16.133p=.001, rs=-.727p=.007 2002 : X^2_{(3)}=3.653p=.609, rs=-.042p=.897 2010 : X^2_{(3)}=5.780p=.123, rs=-.629p=.028 The relative age effect was significant in especially1980 and 2010. In 1980 the preexisting rival star wrestlers were inferred to be significant others for relative age effect of wrestlers.

The Relative Age Effect is explored in 742 Japanese baseball players on the roster of THE PROFESSIONAL BASEBALL ORGANIZATION OF JAPAN in 2002. The cut off date, April 1st in Japan, segments the birth-month distribution of players. Players born after the cut-off date are over-represented, whereas players born before the cut-off date are under-represented. The distribution decreasing from left to right after cut-off date is linear and steep. In Japan, early-births [HAYA-UMARE], whose birth dates are in January, February and March, are less likely to become professional baseball players. Divided by personal traits, high-school graduates rather than university graduates, lower achievers rather than upper achievers, and right-handed throwers rather than left-handed throwers, have higher relative age effects.

The relative age effect (RAE), the advantage of being born early within a cohort, is known to penetrate across sports and countries. In this study gender differences in RAE on the elite sports were analyzed in swimming, track and field, judo, basketball, volleyball and soccer in Japan. In examining RAE, spearman rank-order correlation coefficient and simple linear regression analysis were performed. Soccer ranked first in favor of males in RAE difference between male and female, with volleyball last. The factors that make these two events different with regard to gender are considered from two points of view, player population and exposure to mass media.