Inflammatory markers in type 2 diabetes with vs. without cognitive impairment; a systematic review and meta-analysis

•Levels of BDNF were lower in type 2 diabetes (T2DM) with cognitive impairment (CI).•IL-6, CRP, sVCAM-1 and AGE levels were higher in T2DM with CI.•Increased inflammatory-vascular interactions may be associated with CI in T2DM. People with type 2 diabetes mellitus (T2DM) are at increased risk of mild cognitive impairment and dementia. Systemic inflammation has been proposed as a common risk factor. This study aimed to summarize the clinical data pertaining to peripheral blood inflammatory markers. We identified original peer-reviewed articles reporting blood inflammatory marker concentrations in groups of people with a T2DM diagnosis who have cognitive impairment (CI; including mild cognitive impairment, Alzheimer’s disease, vascular cognitive impairment) vs. normal cognition (NC). Between-group standardized mean differences (SMD) were summarized in random effects meta-analyses. From 2108 records, data were combined quantitatively from 40 studies. Concentrations of interleukin-6 (IL-6; NCI/NNC = 934/3154, SMD 0.74 95% confidence interval [0.07, 1.42], Z5 = 2.15, p = 0.03; I2 = 98.08%), C-reactive protein (CRP; NCI/NNC = 1610/4363, SMD 0.80 [0.50, 1.11], Z14 = 5.25, p