Association of metabolic syndrome and its components with all-cause and cardiovascular mortality in the elderly: A meta-analysis of prospective cohort studies

There is increasing evidence regarding the relationship between metabolic syndrome and mortality. However, previous research examining metabolic syndrome and mortality in older populations has produced mixed results. In addition, there is a clear need to identify and manage individual components of metabolic syndrome to decrease cardiovascular disease (CVD) mortality. In this meta-analysis, we searched the MEDLINE databases using PubMed, Cochrane Library, and EMBASE databases. Based on 20 prospective cohort studies, metabolic syndrome was associated with a higher risk of all-cause mortality [relative risk (RR), 1.23; 95% confidence interval (CI), 1.15–1.32; I(2) = 55.9%] and CVD mortality (RR, 1.24; 95% CI, 1.11–1.39; I(2) = 58.1%). The risk estimates of all-cause mortality for single components of metabolic syndrome were significant for higher values of waist circumference or body mass index (RR, 0.94; 95% CI, 0.88–1.00), higher values of blood glucose (RR, 1.19; 95% CI, 1.05–1.34), and lower values of high-density lipoprotein (HDL) cholesterol (RR, 1.11; 95% CI, 1.02–1.21). In the elderly population, metabolic syndrome was associated with an increased risk of all-cause and CVD mortality. Among the individual components of metabolic syndrome, increased blood glucose and HDL cholesterol levels were significantly associated with increased mortality. However, older obese or overweight individuals may have a decreased mortality risk. Thus, the findings of the current meta-analysis raise questions about the utility of the definition of metabolic syndrome in predicting all-cause mortality and CVD mortality in the elderly population.