Metabolic Syndrome and the Risk of Alzheimer's Disease: A Meta-Analysis

The relationship between metabolic syndrome (MetS) and the risk of Alzheimer's disease (AD) remains unclear. This meta-analysis aims to clarify the prospective association between MetS and AD risk and to explore how individual MetS components contribute to this relationship. Comprehensive searches of MEDLINE, Web of Science, and Embase were conducted up to April 12, 2024. Relevant prospective cohort studies were included. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated to assess the associations. A random-effects model was used to incorporate the potential impact of heterogeneity. Six prospective cohort studies with seven datasets, including 484,994 participants and a follow-up of 3.5 to 13.0 years, were included. The pooled analysis showed no significant association between MetS and AD risk (HR: 0.96, 95% CI: 0.89-1.04, P = 0.37; I² = 0%). Sensitivity and subgroup analyses confirmed these findings. Individual MetS components exhibited varied effects as follows: abdominal obesity was linked to a reduced AD risk (Risk ratio (RR): 0.70, 95% CI: 0.56-0.88, P = 0.002), whereas high blood pressure (BP) (RR: 1.15, 95% CI: 1.04-1.27, P = 0.007) and hyperglycemia (RR: 1.24, 95% CI: 1.08-1.42, P = 0.002) were associated with an increased risk. Low high-density lipoprotein cholesterol and high triglycerides showed no significant associations. This meta-analysis found no significant overall association between MetS and AD risk. However, specific MetS components, such as abdominal obesity, high BP, and hyperglycemia, may influence AD risk differently.