Metabolic Syndrome and the Risk of Mild Cognitive Impairment and Progression to Dementia Follow-up of the Singapore Longitudinal Ageing Study Cohort

IMPORTANCE The association of the metabolic syndrome (MetS) and component cardiovascular risk factors with the risk of developing mild cognitive impairment (MCI) and MCI progression to dementia is not well established. OBJECTIVE To investigate the association of the MetS and its component cardiovascular risk factors with the incidence of MCI and its progression to dementia. DESIGN, SETTING, AND PARTICIPANTS Prospective longitudinal study from September 1, 2003, through December 31, 2009, in communities in 5 districts in the South East region of Singapore. Study participants were a population-based sample of 1519 cognitively normal adults 55 years and older. MAIN OUTCOMES AND MEASURES Prespecified outcomes were incident MCI and MCI progression to dementia. RESULTS The study cohort comprised 1519 participants. Their mean (SD) age was 64.9 (6.8) years, and 64.8%(n = 984) were female. Baseline characteristics associated with an increased risk of incident MCI were MetS (hazard ratio [HR], 1.46; 95% CI, 1.02-2.09), central obesity (HR, 1.41; 95% CI, 1.01-1.98), diabetes mellitus (HR, 2.84; 95% CI, 1.92-4.19), dyslipidemia (HR, 1.48; 95% CI, 1.01-2.15), and 3 or more component cardiovascular risk factors (HR, 1.58; 95% CI, 1.13-2.33). Baseline characteristics associated with an increased risk of MCI progression to dementia were MetS (HR, 4.25; 95% CI, 1.29-14.00), diabetes mellitus (HR, 2.47; 95% CI, 1.92-4.19), and 3 or more component cardiovascular risk factors (HR, 4.92; 95% CI, 1.39-17.4). CONCLUSIONS AND RELEVANCE The MetS was associated with an increased incidence of MCI and progression to dementia. Identifying individuals with diabetes mellitus or the MetS with or without MCI is a promising approach in early interventions to prevent or slow progression to dementia.