title: Biochemical indicators of vitamin B12 and folate insufficiency and cognitive decline.
abstract: BACKGROUND
  In some prospective studies, associations of serum vitamin B(12) and homocysteine concentrations with cognitive decline have been reported but few have examined the role of methylmalonic acid, a more specific marker of vitamin B(12) deficiency than homocysteine.
  
  
  OBJECTIVE
  The aim of the study was to determine whether serum concentrations of vitamin B(12) or selected metabolites are related to cognitive decline.
  
  
  METHODS
  A total of 516 subjects were selected in a stratified random sampling design from among Chicago Health and Aging Project participants for clinical evaluation. We used linear mixed models to examine the association of blood markers of vitamin B(12) status to change in cognitive scores over 6 years. Cognitive function was assessed every 3 years and measured as the sum of standardized scores on four tests.
  
  
  RESULTS
  Probable vitamin B(12) deficiency was observed in 14.2% of the sample. Elevated serum concentrations of homocysteine were present in 19.2% of subjects, and of methylmalonic acid, in 36.4%. Higher serum methylmalonic acid concentrations were predictive of faster rates of cognitive decline (beta = -0.00016, SE = 0.0001, p = 0.004) and higher serum vitamin B(12) concentrations were associated with slower rates of cognitive decline (beta = +0.00013, SE < 0.0001, p = 0.005) in multivariable adjusted mixed models. Serum concentrations of homocysteine had no relationship to cognitive decline.
  
  
  CONCLUSIONS
  Serum methylmalonic acid and vitamin B(12) concentrations may be the more important risk factors for cognitive decline when compared to serum homocysteine concentrations, particularly in older populations exposed to food fortification and possible supplements containing folic acid.
authors.affiliation: Department of Clinical Nutrition, Rush University Medical Center, Chicago, IL 60612, USA. ctangney@rush.edu
authors.forename: Christine C
authors.initials: CC
authors.lastname: Tangney
authors.forename: Yuxiao
authors.initials: Y
authors.lastname: Tang
authors.forename: Denis A
authors.initials: DA
authors.lastname: Evans
authors.forename: Martha Clare
authors.initials: MC
authors.lastname: Morris
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D003072:Cognition Disorders / Q000097:blood* / Q000150:complications / Q000175:diagnosis; D015331:Cohort Studies; D005260:Female; D005492:Folic Acid / Q000097:blood; D005494:Folic Acid Deficiency / Q000097:blood* / Q000150:complications / Q000175:diagnosis; D006801:Humans; D007202:Indicators and Reagents; D008297:Male; D008764:Methylmalonic Acid / Q000097:blood; D012307:Risk Factors; D014805:Vitamin B 12 / Q000097:blood; D014806:Vitamin B 12 Deficiency / Q000097:blood* / Q000150:complications / Q000175:diagnosis
chemical_list: D015415:Biomarkers; D007202:Indicators and Reagents; D008764:Methylmalonic Acid; D005492:Folic Acid; D014805:Vitamin B 12