Vascular risk factors, such as type 2 diabetes mellitus, hypertension, dyslipidemia and obesity, have been associated with an increased risk of cognitive dysfunction, particularly in the elderly. The aim of this systematic review was to compare these risk factors with regard to the nature and magnitude of the associated cognitive decrements. Cross-sectional and longitudinal studies that assessed cognitive functioning in non-demented persons in relation to diabetes/impaired glucose metabolism (k = 36), hypertension (k = 24), dyslipidemia (k = 7) and obesity (k = 6) and that adjusted or matched for age, gender and education were included. When possible, effect sizes (Cohen's d) were computed per cognitive domain. Diabetes and hypertension were clearly associated with cognitive decrements; the results for obesity and dyslipidemia were less consistent. Effect sizes were moderate (median approximately -0.3) for all risk factors. Decline was found in all cognitive domains, although the effects on cognitive speed, mental flexibility and memory were most consistent. Methodological aspects of included studies and implications of these findings are discussed.

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The small but robust and consistent effects of WMHs on all cognitive domains suggest a more global effect on cognition than previously thought. Progression of WMHs was associated with even worse cognitive functioning, most pronounced in attention and executive functioning.