Birthdate, Relative Age and Whoever wishes to investigate medicine - - PDF document

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Birthdate, Relative Age and Athlete Development

Joe Baker

Lifespan Health & Performance Laboratory York University, Toronto, Canada

Date of Birth and Development

“Whoever wishes to investigate medicine properly, should proceed thus: in the first place to consider the seasons of the year, and what effects each of them produces for they are not at all alike, but differ much from themselves in regard to their changes.” Hippocrates (400BC)

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Date of Birth and Development

Hippocrates (400BC)

Season of Birth Research SOB related to: Schizophrenia/Bipolar Disorder Anorexia Nervosa/Bulimia Obesity Myopia Longevity

Lifespan Health and Performance Laboratory

Season of birth effects relate to seasonal environments experienced during gestation which have the potential to significantly influence healthy development. Thought to be driven by biological processes.

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Relative age effects relate to differences perceived to exist among individuals due to differences in their age compared to peers. Thought to be driven by socially-constructed processes.

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Date of Birth and Development

Relative Age refers to age compared to others in the same cohort or age group.

August 2007 July 2007 June 2007 May 2007 April 2007 March 2007 February 2007 January 2007 December 2006 November 2006 October 2006 September 2006

Relative Age Effects

In education

3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Relative Age (Birth-Date Quartiles) Pupil Attainment Physical Education Mathematics Science School Year 7 School Year 8 School Year 9 Quartile 1 = Sep - Nov Quartile 2 = Dec - Feb Quartile 3 = Mar - May Quartile 4 = Jun - Aug

(Cobley et al., in press)

Relative Age Effects

In education

• Attainment scores (Bell et al., 1997; Cobley et al., in press)
• Gifted and talented (Cobley et al., in press; Sharp, 1995;

Thompson, 1971)

• Learning disabilities (Bookbinder, 1967; Cobley et al., in

press; Wilson, 2000)

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3 Relative Age Effects

In sports

Relative Age Effects

In sports

50 100 150 200 250 300 350 400 Jan-Mar Apr-Jun Jul-Sep Oct-Dec

Baker & Logan (2007) BJSM NHL Draftees (Canadian and American Data)

Relative Age Effects

In sports

50 100 150 200 250 300 Jan-Mar Apr-Jun Jul-Sep Oct-Dec

Cote, MacDonald, Baker & Abernethy (2006) JSS MLB (American Data)

Relative Age Effects

In sports

0% 5% 10% 15% 20% 25% 30% 35% 40% 1 2 3 4

NBL Rugby League Rugby Union AFL

Australian Data Abernethy & Farrow (2005) ISSP

4 Relative Age Effects

In sports

Germany (Handball data) Schorer, Cobley, Büsch, Bräutigam, & Baker (in prep.)

10 20 30 40 50 D-squad D/C-squad C-squad B-squad A-squad Q1 Q2 Q3 Q4

Relative Age Effects

In sports

20 40 60 80 100 120 140 Jan-Mar Apr-Jun Jul-Sep Oct-Dec

Cote, MacDonald, Baker & Abernethy (2006) JSS NBA (American Data)

Relative Age Effects

In sports

10 20 30 40 50 60 Jan-Mar Apr-Jun Jul-Sep Oct-Dec

Cote, MacDonald, Baker & Abernethy (2006) JSS PGA (American Data)

0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% Jan - Mar Apr - Jun Jul - Sep Oct - Dec

Relative Age Effects

In sports

Wattie, Baker, Cobley & Montelpare (2007) IJSP Women’s Hockey (Canadian data)

5 Relative Age Effects

In sports

• Elite athlete status
• Gifted and talented (Cobley, Abraham & Baker, in press)
• Representative sport (Baker et al., under review)

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Where do relative age effects come from?

• Historical examinations

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RAE History: Canadian NHL Players

20 40 60 80 100 120 140 <1900 1901-1905 1906-1910 1911-1915 1916-1920 1921-1925 1926-1930 1931-1935 1936-1940 1941-1945 1946-1950 1951-1955 1956-1960 1961-1965 1966-1970 1971-1975 1976-1980 Jan - Mar Apr - June July - Sept Oct - Dec ** ** ** ** **

Wattie, Baker, Cobley & Montelpare (2007) IJSP

RAE History: German Soccer Players

25 50 75 100 125 150 175 200 1935 and below 1936- 1940 1941- 1945 1946- 1950 1951- 1955 1956- 1960 1961- 1965 1966- 1970 1971- 1975 1976- 1980 1981 and above* Quartile 1 Quartile 2 Quartile 3 Quartile 4

Cobley, Schorer & Baker (2007) Under Review

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Where do relative age effects come from?

• Historical examinations
• Causal hypotheses

1) Maturational Factors

– Baker et al., under review

Lifespan Health and Performance Laboratory

Where do relative age effects come from?

• Historical examinations
• Causal hypotheses

1) Maturational Factors 2) Psychological Factors

– Positive appraisal from parents & coaches (Pygmalion Effect) – Relatively younger players dropout early (Barnsley & Thompson, 1988)

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Where do relative age effects come from?

• Historical examinations
• Causal hypotheses

1) Maturational Factors 2) Psychological Factors 3) Experiential Factors

–

• Cf. Vaeyens et al. (2005) and Baker et al. (under

review) Lifespan Health and Performance Laboratory

Relative Age Implications

• Achievement and attainment in education and sport
• Overall physical activity participation

– Dropout (Barnsley & Thompson 1988; Helsen et al., 1998)

• Impact on self-perceptions, self-appraisals and motivation

– Self-esteem (Barnsley et al., 2004) – School Attendance (Carroll, 1992; Cobley et al., in press)

• Adolescent mortality

– Youth Suicide (Thompson, Barnsley & Dyck, 1999)

7 Is it always an advantage to be relatively older?

• Relative age and injury

0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% 40.0% 45.0% House Intermediate A AA AAA Q1 Q4

Wattie et al. Pediatrics, 2007

Is it always an advantage to be relatively older?

• Relative age and injury
• Relative age and draft order

– Relatively younger athletes were more sought after in the NHL draft (Baker & Logan, 2007)

Solutions?

• Re-adjustment of age ranges
• Teacher/Coach Education

– Cobley et al (2007)

1 2 3 4 Attainment

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Solutions?

• Re-adjustment of age ranges
• Teacher/Coach Education

– Cobley et al (2007)

1 2 3 4 Attainment

On-going Research

– Relative age and PA/obesity? – Relative age in talent identification? – Relative age and psychological development? – Moderators of the relative age effect? – Causes/Solutions?