Darwinian Selection Discriminates Young Athletes: the Relative Age Effect in Relation to Sporting Performance Johan Jakobsson1* , A
Jakobsson et al. Sports Medicine - Open (2021) 7:16 https://doi.org/10.1186/s40798-021-00300-2 ORIGINAL RESEARCH ARTICLE Open Access Darwinian Selection Discriminates Young Athletes: the Relative Age Effect in Relation to Sporting Performance Johan Jakobsson1* , A. Lennart Julin2, Glenn Persson1 and Christer Malm1 Abstract Background: The relative age effect (RAE) is a worldwide phenomenon, allowing sport participation and elite selection to be based on birthdate distribution. Negative consequences include both a narrow, non-optimal elite selection and negative health effects on entire populations. This study investigated the RAE and athletic performance in multiple individual sports in Sweden. Methods: Birthdates of athletes born between the years 1922 and 2015 were collected across 4-month periods (tertiles: T1, T2, T3) from cross-country skiing (N = 136,387), orienteering (N = 41,164), athletics (N = 14,503), alpine skiing (N = 508), E-sports (N = 47,030), and chess (N = 4889). In total, data from 244,560 athletes (women: N = 79, 807, men: N = 164,753) was compared to the complete parent population of 5,390,954 births in Sweden during the same years. Chi-squared statistics compared parent and cohort distributions stratified by sport, sex, and age. Results: A significantly skewed distribution of birthdates was present in all sports, both sexes, and most age groups. The largest RAEs are seen in children where T1 often constitutes 40–50% and T3, 20–25% of the population. In E-sports, an inversed RAE was seen in adults. In most investigated sports, birthdate distribution was correlated to performance in children but not in adults.
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