The Association between Carotid Intima-Media Thickness and Cognitive Impairment: A Systematic Review and Meta-Analysis

<b><i>Background:</i></b> Emerging evidence suggests that cognitive impairment (CI) and different etiologies of dementia, including Alzheimer’s disease (AD), are associated with vascular risk factors and atherosclerosis. In clinical practice, carotid intima-media thickness (CIMT) measured by ultrasonography may be a marker of atherosclerosis. Many studies report increased CIMT in patients with dementia and CI although a firm association has not yet been established. <b><i>Aim:</i></b> This systematic review and meta-analysis were conducted to study the relationship between CIMT, dementia, and CI. <b><i>Methods:</i></b> The literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and included the following databases: Medline, Embase, Cochrane Library, and Epistemonikos. The search spanned from 2000 to 2020 and was limited to English and Scandinavian languages. <b><i>Results:</i></b> The main analysis of CIMT in subjects with CI compared to subjects with no cognitive impairment (NCI) included 12 studies; 1,089 subjects with CI and 5,223 with NCI. There was no significant difference in CIMT between the CI and NCI groups. However, subgroup analyses revealed significantly higher CIMT in the mild cognitive impairment (MCI) and dementia groups than the NCI group. In addition, patients with dementia had increased CIMT compared to patients with MCI, and patients with AD demonstrated higher CIMT than those with vascular cognitive impairment (VCI). <b><i>Conclusion:</i></b> CIMT may be higher in subjects with CI than in cognitively healthy subjects although no significant difference was observed in our main analysis. CIMT was higher in the dementia group than the MCI group and in the AD group compared to the VCI group.