Abstract: Objective To study the association between metabolic syndrome (MS) and mild cognitive impairment (MCI) among the elderly.Methods A 1:2 amatched nested case-control study was conducted among the old people aged 60 and over,who participated in 2004-2005 baseline survey and completed biochemical tests.The impact of MS and components of MS on the risk of developing MCIere analyzed after adjusting for age,gender,and education.Results Hyperglycemia(odds ratioOR=2.9,95% confidence intervalCI:1.4-5.9),hypertension(OR=2.5,95% CI:1.3-4.8),hyperlipidemia(OR=2.2,95% CI:1.1-4.1) showed significant effects on the development of MCI.Comparedith the baseline group(normal orith one component of MS),the risk of MCI for groupⅠ(ith any two components of MS) and group Ⅱ(ith any three or more components of MS)ere 2.3 folds (OR=2.3,95% CI:1.2-4.6) and 3.5 folds (OR=3.5,95%CI:1.7-7.5) higher,respectively.Conclusion Hyperglycemia,hypertension,and hyperlipidemia are risk factors of MCI.The risk of MCI increases among the old peopleith increased components of MS.