Association between metabolic syndrome and cognitive impairment: a meta-analysis of analytical observational studies

The potential link between metabolic syndrome (MetS) and the risk of dementia or cognitive impairment remains uncertain. This study aimed to assess the association between MetS and cognitive decline through a comprehensive review and meta-analysis of the existing literature. A systematic search was conducted in Medline (PubMed), Web of Science, Scopus and Embase up to January 2023. Eligible studies included cohort and case-control designs. Statistical analyses were performed using STATA version 17. A total of 20 studies comprising 5,727,594 participants were included. The pooled relative risk (RR) of cognitive impairment among individuals with MetS was 1.34 (95% CI: 1.25–1.43), indicating a significant association. Subgroup analyses revealed that the NCEP-ATP III criteria more effectively identified this relationship compared to other diagnostic methods. The association appeared strongest in Asian populations, followed by European and American groups. This meta-analysis supports a significant association between MetS and cognitive impairment. Geographic variation in the strength of this relationship may be influenced by differences in diagnostic criteria and lifestyle factors. The findings underscore the importance of early screening and the development of region-specific public health interventions to mitigate cognitive decline in individuals with MetS.