title: A meta-analysis of cognitive functioning in nondemented adults with type 2 diabetes mellitus.
abstract: OBJECTIVE
  The current investigation sought to determine the pattern and magnitude of cognitive functioning deficits in persons with type 2 diabetes mellitus without dementia using meta-analysis to consolidate findings in the literature.
  
  
  METHODS
  MedLine and PsychInfo databases were searched to identify studies of cognitive functioning in persons with type 2 diabetes. Effect sizes (Cohen's d) were calculated for the differences in cognitive functioning between subjects with type 2 diabetes and controls without diabetes on classified cognitive abilities. Average d values were calculated for all cognitive abilities across studies.
  
  
  RESULTS
  Twenty-five studies meeting the inclusion criteria were identified. Persons with type 2 diabetes performed significantly lower than controls without diabetes (p<0.05) on all cognitive abilities evaluated, with effect sizes ranging from -0.14 to -0.37. The largest effect sizes were processing speed (with motor task demands), M -0.37 (95% CI, -0.41 to -0.32), and divided attention/shifting, M -0.36 (95% CI, -0.42 to -0.31).
  
  
  CONCLUSIONS
  Type 2 diabetes leads to mild to moderate deficits in all measured cognitive abilities. There was a lack of published studies investigating type 2 diabetes-associated variables; therefore, additional meta-analyses investigating the impact of these variables on cognitive functioning in type 2 diabetes could not be performed. As such, data from individual studies must be reported consistently to allow for investigation of variables that may affect the relationship between type 2 diabetes and cognitive functioning. Given the present findings, clinicians working with patients with type 2 diabetes should be alerted to the possibility of cognitive changes that could impact type 2 diabetes treatment management or require referral for neuropsychological assessment.
authors.affiliation: Department of Psychology, University of Windsor, Windsor, Ontario. Electronic address: monettem@uwindsor.ca.
authors.forename: Michelle C E
authors.initials: MC
authors.lastname: Monette
authors.affiliation: Department of Psychology, University of Windsor, Windsor, Ontario.
authors.forename: Anne
authors.initials: A
authors.lastname: Baird
authors.affiliation: Department of Psychology, University of Windsor, Windsor, Ontario.
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Jackson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003072:Cognition Disorders / Q000378:metabolism*; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests
keywords: cognitive abilities; cognitive functioning; diabète de type 2; fonctionnement cognitif; habiletés cognitives; meta-analysis; méta-analyse; type 2 diabetes