title: Association between metabolic syndrome and cognitive decline: a systematic review of prospective population-based studies.
abstract: OBJECTIVE
  The association between metabolic syndrome (MS) and the risk of cognitive impairment or dementia remains unclear. In this article, we systematically review studies on the risk of cognitive disorders in patients with MS to determine the strength of the association between MS and cognitive decline.
  
  
  METHODS
  Electronic databases through December 2009 were searched to identify prospective population-based studies that examined the association between MS and risk of cognitive disorders. Two reviewers used a standardised form to collect data and assess eligibility. The quality of study was assessed by the Newcastle-Ottawa Scale.
  
  
  RESULTS
  We found nine eligible studies that involve 19 876 participants. All studies but two indicate that MS is associated with cognitive decline (from one-fold to more than two-fold increase in risk). It seems that MS may be associated with cognitive impairment (positive results in three of five) and vascular dementia (positive results in two of three), whereas three studies involving patients with Alzheimer's disease (AD) did not find the association between MS and AD. When examining the association of the individual risk factors of the MS and cognition in seven eligible studies, glucose (three studies) and hypertension (three studies) showed positive results associated with cognitive decline.
  
  
  CONCLUSIONS
  The MS may be associated with cognitive impairment and vascular dementia but not for AD, which need to be further investigated with high-quality studies.
authors.affiliation: Stroke Clinical Research Unit, Department of Neurology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan Province, P. R. China.
authors.forename: Zilong
authors.initials: Z
authors.lastname: Hao
authors.affiliation: Stroke Clinical Research Unit, Department of Neurology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan Province, P. R. China.
authors.forename: Bo
authors.initials: B
authors.lastname: Wu
authors.affiliation: Stroke Clinical Research Unit, Department of Neurology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan Province, P. R. China.
authors.forename: Deren
authors.initials: D
authors.lastname: Wang
authors.affiliation: Stroke Clinical Research Unit, Department of Neurology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan Province, P. R. China.
authors.forename: Ming
authors.initials: M
authors.lastname: Liu