USP Araba Sport Clinic, Vitoria-Gasteiz, Basque Country, Spain.
J Sports Sci. 2009 Sep;27(11):1153-8. doi: 10.1080/02640410903220328.
The relative age effect is an uneven distribution of birth date favouring subjects born in the initial months of a selection year. This study compared the birth-date distributions between several subgroups of Basque football players to identify whether the relative age effect is influenced by age and/or skill level. The study comprised 13,519 players including 114 senior professionals from the Spanish league's AC Bilbao over 21 seasons; over the season 2005-2006, it comprised elite youth (n=189) from the same club's academy; regional youth (n=4382) U11-U14 locally federated players; school youth (n=8834) U10-U11 locally registered school district players. Differences between the observed and expected birth-date distributions were tested based on data from the general Basque male population. Significant chi-square values were followed up by calculating odds ratios and 95% confidence intervals (CI) for the quartile and half-year distributions to examine subgroup differences in the relative age effect. Birth-date distributions of all groups of players showed a significant bias towards early birth in the selection year compared with the reference population (senior, chi-2(3) = 24.4, P < 0.001; elite youth, chi-2(3) = 59.1, P < 0.001; regional youth, chi-2(3) = 41.4, P < 0.001; school youth, chi-2(3) = 40.9, P < 0.001). Between-group comparison revealed that the relative age effect incidence progressively increased with a higher level of involvement in youth football. This bias represents a significant loss of potential youth football talent.
相对年龄效应是指出生日期分布不均匀，有利于在选拔年度初始几个月出生的受试者。本研究比较了巴斯克足球运动员的几个亚组的出生日期分布，以确定相对年龄效应是否受年龄和/或技能水平的影响。该研究包括 13519 名球员，其中包括西班牙联赛毕尔巴鄂竞技队的 114 名高级职业球员，在 21 个赛季中；在 2005-2006 赛季，它包括来自同一俱乐部学院的精英青年（n=189）；地区青年（n=4382）U11-U14 本地联合会球员；学校青年（n=8834）U10-U11 本地注册学区球员。根据一般巴斯克男性人口的数据，测试了观察到的和预期的出生日期分布之间的差异。对显著的卡方值进行了跟进，计算了四分位和半年分布的优势比和 95%置信区间（CI），以检查相对年龄效应的亚组差异。与参考人群相比，所有球员组的出生日期分布在选拔年度都存在明显的早生偏倚（高级，chi-2(3)=24.4，P<0.001；精英青年，chi-2(3)=59.1，P<0.001；地区青年，chi-2(3)=41.4，P<0.001；学校青年，chi-2(3)=40.9，P<0.001）。组间比较表明，相对年龄效应的发生率随着青年足球参与度的提高而逐渐增加。这种偏差代表了青年足球人才的重大损失。
