Relationship between Insulin Levels and Nonpsychotic Dementia: A Systematic Review and Meta-Analysis

Abstract

Objectives To explore the relationship between insulin levels and nonpsychotic dementia. Methods Six electronic databases (PubMed, Cochrane, SCI, CNKI, VIP, and Wanfang) were searched from January 1, 2007, to March 1, 2017. Experimental or observational studies that enrolled people with nonpsychotic dementia or abnormal insulin levels in which insulin levels or MMSE scores (events in nonpsychotic dementia) were the outcome measures. Random-effects models were chosen for this meta-analysis. Sample size, mean, s.d., and events were primarily used to generate effect sizes (with the PRIMA registration number CRD42017069860). Results 50 articles met the final inclusion criteria. Insulin levels in cerebrospinal fluid were lower (Hedges' g = 1.196, 95% CI = 0.238 to 2.514, and P = 0.014), while the levels in peripheral blood were higher in nonpsychotic dementia patients (Hedges' g = 0.853 and 95% CI = 0.579 to 1.127), and MMSE scores were significantly lower in the high insulin group than in the healthy control group (Hedges' g = 0.334, 95% CI = 0.249 to 0.419, and P = 0.000). Conclusions Our comprehensive results indicate that blood insulin levels may increase in patients with nonpsychotic dementia.

Mechanisms of diabetes and dementia

“…These are present particularly in areas associated with memory and learning, including the hypothalamus, amygdala, hippocampus, caudate and putamen . A recent meta‐analysis looking at the relationship between insulin levels and dementia found that blood insulin levels may increase in patients with non‐psychotic dementia . Additionally, changes in insulin levels also affect uptake of glucose by neurones and its metabolism via GLUT 4 pathways involved in cognition …”