Impact of Insulin Sensitizers on the Incidence of Dementia: A Meta-Analysis

Abstract

Background: Abundant evidence from epidemiological and clinical studies has proven that diabetes mellitus (DM) is correlated with an increased incidence of dementia and Alzheimer's disease (AD). Insulin resistance is considered to play an important role in the associations between DM and dementia. However, whether insulin sensitizer drugs are effective in preventing dementia still remains unclear. Methods: Electronic searches of PubMed, EMBASE, Google Scholar, and the ISI Web of Science were conducted to identify studies that reported about the associations between insulin sensitizers and the incidence of dementia. The included studies were reviewed, and a meta-analysis was performed using STATA to determine the combined relative risk (RR) for the incidence of dementia when using insulin sensitizers. Subgroup analysis and meta regression were also conducted. Results: In total, nine comparisons out of six studies were qualified for inclusion, and data from 544,093 participants were evaluated. The results of the meta-analysis revealed a combined RR of 0.78 (95% CI 0.64-0.95, p = 0.015) for the incidence of dementia when using insulin sensitizers. The incidence rate of dementia was reduced with either metformin (RR 0.79, 95% CI 0.62-1.01, p = 0.064) or thiazolidinediones (RR 0.75, 95% CI 0.56-1.00, p = 0.050), both with a marginal trend toward significance. Conclusions: The results indicate that insulin sensitizer drugs might provide protection against incident dementia. Controlled studies with large samples should be conducted to further confirm these conclusions and provide information for clinical strategies.