title: Exposure to air pollution and cognitive functioning across the life course--A systematic literature review.
abstract: OBJECTIVE
  Air pollution is associated with increased risk of respiratory, cardiovascular and cerebrovascular disease, but its association with cognitive functioning and impairment is unclear. The aim of this systematic review was to examine whether a relationship exists between these variables across the life course.
  
  
  METHODS
  We searched Web of Knowledge, Pubmed, SciVerse Scopus, CINAHL, PsychInfo and Science Direct up to October 2015 to identify studies that investigated the association between air pollution and performance on neurocognitive tests.
  
  
  RESULTS
  Variations in exposure assessment and outcome measures make meta-analysis impossible. Thirty one studies published between 2006 and 2015, from the Americas (n=15), Asia (n=5) and Europe (n=11), met the criteria for inclusion. Many showed weak but quantified relationships between various air pollutants and cognitive function. Pollution exposure in utero has been associated with increased risk of neuro-developmental delay. Exposure in childhood has been inversely associated with neuro-developmental outcomes in younger children and with academic achievement and neurocognitive performance in older children. In older adults, air pollution has been associated with accelerated cognitive decline.
  
  
  CONCLUSIONS
  The evidence to date is coherent in that exposure to a range of largely traffic-related pollutants has been associated with quantifiable impairment of brain development in the young and cognitive decline in the elderly. There is insufficient evidence at present to comment on consistency, in view of the different indices of pollution and end-points measured, the limited number of studies, and the probability at this stage of publication bias. However, plausible toxicological mechanisms have been demonstrated and the evidence as a whole suggests that vehicular pollution, at least, contributes to cognitive impairment, adding to pressure on governments and individuals to continue to reduce air pollution.
authors.affiliation: Faculty of Education, Health and Wellbeing, University of Wolverhampton, Wolverhampton, UK.
authors.forename: Angela
authors.initials: A
authors.lastname: Clifford
authors.affiliation: Faculty of Education, Health and Wellbeing, University of Wolverhampton, Wolverhampton, UK; Post Graduate Academic Institute of Medicine, University of Wolverhampton, Wolverhampton, UK.
authors.forename: Linda
authors.initials: L
authors.lastname: Lang
authors.affiliation: Faculty of Education, Health and Wellbeing, University of Wolverhampton, Wolverhampton, UK; Post Graduate Academic Institute of Medicine, University of Wolverhampton, Wolverhampton, UK. Electronic address: r.chen@wlv.ac.uk.
authors.forename: Ruoling
authors.initials: R
authors.lastname: Chen
authors.affiliation: Centre for Research on Ageing, Health and Wellbeing, The Australian National University, Australia.
authors.forename: Kaarin J
authors.initials: KJ
authors.lastname: Anstey
authors.affiliation: School of Applied Health Sciences, University of Aberdeen, Aberdeen, UK.
authors.forename: Anthony
authors.initials: A
authors.lastname: Seaton
mesh_terms: D000367:Age Factors; D000397:Air Pollution / Q000009:adverse effects*; D003071:Cognition; D006801:Humans; D001335:Vehicle Emissions / Q000633:toxicity
chemical_list: D001335:Vehicle Emissions
keywords: Air pollution; Cognition; Neurodevelopment