title: Relationship between physical activity and cognitive function in apparently healthy young to middle-aged adults: A systematic review.
abstract: OBJECTIVE
  There is increasing evidence that physical activity (PA) positively affects cognitive function (CF). Existing research has focussed on this association in children and the elderly, with less research available in young to middle-aged adults who constitute a substantial proportion of the population.
  
  
  METHODS
  A systematic review investigating the relationship between habitual PA (≥12 months) and CF in young to middle-aged adults (18-50 years).
  
  
  METHODS
  A search was conducted using AMED, CINAHL, MEDLINE, PsychINFO, AUSPORT MED and SPORTDiscus databases. Eligible studies had to report descriptive statistics for CF and PA levels in healthy participants 18-50 years. Effect sizes (ES) (Hedges g) were calculated where possible.
  
  
  RESULTS
  The initial search netted 26,988 potentially relevant manuscripts, with four more identified through hand searching. Fourteen were included for review. A range of validated platforms assessed CF across three domains: executive function (12 studies), memory (four studies) and processing speed (seven studies). Habitual PA was assessed via questionnaire/self-report methods (n=13, 8 validated) or accelerometers (n=1). In studies of executive function, five found a significant ES in favour of higher PA, ranging from small to large. Although three of four studies in the memory domain reported a significant benefit of higher PA, there was only one significant ES, which favoured low PA. Only one study examining processing speed had a significant ES, favouring higher PA.
  
  
  CONCLUSIONS
  A limited body of evidence supports a positive effect of PA on CF in young to middle-aged adults. Further research into this relationship at this age stage is warranted.
authors.affiliation: Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Australia.
authors.forename: Eka Peng
authors.initials: EP
authors.lastname: Cox
authors.affiliation: Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Australia; School of Human Movement Studies, Charles Sturt University, Australia.
authors.forename: Nicholas
authors.initials: N
authors.lastname: O'Dwyer
authors.affiliation: Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Australia.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Cook
authors.affiliation: Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Australia.
authors.forename: Melanie
authors.initials: M
authors.lastname: Vetter
authors.affiliation: Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Australia; Academic Department of Adolescent Medicine, The University of Sydney, Australia.
authors.forename: Hoi Lun
authors.initials: HL
authors.lastname: Cheng
authors.affiliation: Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Australia; Charles Perkins Centre, The University of Sydney, Australia.
authors.forename: Kieron
authors.initials: K
authors.lastname: Rooney
authors.affiliation: Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Australia; Charles Perkins Centre, The University of Sydney, Australia. Electronic address: helen.oconnor@sydney.edu.au.
authors.forename: Helen
authors.initials: H
authors.lastname: O'Connor
mesh_terms: D000293:Adolescent; D000328:Adult; D003071:Cognition / Q000502:physiology*; D056344:Executive Function / Q000502:physiology*; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D055815:Young Adult
keywords: Adult; Cognition; Exercise; Physical activity; Young adult