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J Int Neuropsychol Soc. 2014 Mar;20(3):278-91. doi: 10.1017/S1355617713001483. Epub 2014 Feb 20.

Magnitude of cognitive dysfunction in adults with type 2 diabetes: a meta-analysis of six cognitive domains and the most frequently reported neuropsychological tests within domains.

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1 Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
3 Department of Neurology, Rudolf Magnus Institute of Neuroscience, University Medical Center, Utrecht, The Netherlands.
4 Department of Physical Medicine and Rehabilitation, Johns Hopkins School of Medicine, Baltimore, Maryland.
2 Welch Center for Prevention, Epidemiology, and Clinical Research, Baltimore, Maryland.


The objectives were to conduct a meta-analysis in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards to determine effect sizes (Cohen's d) for cognitive dysfunction in adults with type 2 diabetes, relative to nondiabetic controls, and to obtain effect sizes for the most commonly reported neuropsychological tests within domains. Twenty-four studies, totaling 26,137 patients (n = 3351 with diabetes), met study inclusion criteria. Small to moderate effect sizes were obtained for five of six domains: motor function (3 studies, n = 2374; d = -0.36), executive function (12 studies, n = 1784; d = -0.33), processing speed (16 studies, n = 3076; d = -0.33), verbal memory (15 studies, n = 4,608; d = -0.28), and visual memory (6 studies, n = 1754; d = -0.26). Effect size was smallest for attention/concentration (14 studies, n = 23,143; d = -0.19). The following tests demonstrated the most notable performance decrements in diabetes samples: Grooved Pegboard (dominant hand) (d = -0.60), Rey Auditory Verbal Learning Test (immediate) (d = -0.40), Trails B (d = -0.39), Rey-Osterreith Complex Figure (delayed) (d = -0.38), Trails A (d = -0.34), and Stroop Part I (d = -0.28). This study provides effect sizes to power future epidemiological and clinical diabetes research studies examining cognitive function and to help inform the selection of neuropsychological tests.

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