Impact of Worsened Metabolic Syndrome on the Risk of Dementia: A Nationwide Cohort Study

BACKGROUND The relationship of alteration of metabolic syndrome (MetS) with dementia remains unclear. The purpose of study was to evaluate the association between dynamic change in MetS status around a 5-year period and dementia. METHODS AND RESULTS The cohort study was conducted from the Taiwanese Survey on Prevalence of Hypertension, Hyperglycemia, and Hyperlipidemia in 2002, with follow-up in 2007. The sample was subsequently linked to the National Health Insurance Research Database. Participants were divided into 3 groups: persistent MetS (MetS both in 2002 and 2007); nonpersistent MetS (MetS either in 2002 or 2007); and non-MetS (MetS neither in 2002 nor 2007). Furthermore, the individuals with nonpersistent MetS were categorized as improved MetS (MetS in 2002 but not in 2007) and worsened MetS (MetS not in 2002 but in 2007). Each participant was tracked until the end of 2011 to identify the development of dementia. In total, 3458 participants aged 40 to 80 years were included. Up to 10 years and 31 741 person-years of follow-up, 76 patients developed dementia. Only a relationship was found between the nonpersistent MetS and dementia (adjusted hazard ratio=1.93; 95% confidence interval =1.17-3.19; P=0.010). Moreover, a significantly higher dementia risk was observed in patients with worsened MetS (adjusted hazard ratio=2.22; 95% confidence interval=1.32-3.72; P=0.003), but not those with persistent (P=0.752) or improved (P=0.829) MetS. Similar results were detected in participants aged ≥65 years. CONCLUSIONS Patients with worsened MetS had an increased dementia risk during the 10-year follow-up period in a population-based sample.