title: Serum brain-derived neurotrophic factor and the risk for dementia: the Framingham Heart Study.
abstract: OBJECTIVE
  In animal studies, brain-derived neurotrophic factor (BDNF) has been shown to impact neuronal survival and function and improve synaptic plasticity and long-term memory. Circulating BDNF levels increase with physical activity and caloric restriction, thus BDNF may mediate some of the observed associations between lifestyle and the risk for dementia. Some prior studies showed lower circulating BDNF in persons with Alzheimer disease (AD) compared with control participants; however, it remains uncertain whether reduced levels precede dementia onset.
  
  
  OBJECTIVE
  To examine whether higher serum BDNF levels in cognitively healthy adults protect against the future risk for dementia and AD and to identify potential modifiers of this association.
  
  
  METHODS
  Framingham Study original and offspring participants were followed up from 1992 and 1998, respectively, for up to 10 years. We used Cox models to relate BDNF levels to the risk for dementia and AD and adjusted for potential confounders. We also ran sensitivity analyses stratified by sex, age, and education, as well as related BDNF genetic variants to AD risk. This community-based, prospective cohort study involved 2131 dementia-free participants aged 60 years and older (mean [SD] age, 72 [7] years; 56% women).
  
  
  METHODS
  Ten-year incidence of dementia and AD.
  
  
  RESULTS
  During follow-up, 140 participants developed dementia, 117 of whom had AD. Controlling for age and sex, each standard-deviation increment in BDNF was associated with a 33% lower risk for dementia and AD (P = .006 and P = .01, respectively) and these associations persisted after additional adjustments. Compared with the bottom quintile, BDNF levels in the top quintile were associated with less than half the risk for dementia and AD (hazard ratio, 0.49; 95% CI, 0.28-0.85; P = .01; and hazard ratio, 0.46; 95% CI, 0.24-0.86; P = .02, respectively). These associations were apparent only among women, persons aged 80 years and older, and those with college degrees (hazard ratios for AD: 0.65, [95% CI, 0.50-0.85], P = .001; 0.63 [95% CI, 0.47-0.85], P = .002; and 0.27 [95% CI, 0.11-0.65], P = .003, respectively). Brain-derived neurotrophic factor genetic variants were not associated with AD risk.
  
  
  CONCLUSIONS
  Higher serum BDNF levels may protect against future occurrence of dementia and AD. Our findings suggest a role for BDNF in the biology and possibly in the prevention of dementia and AD, especially in select subgroups of women and older and more highly educated persons.
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts2The Framingham Heart Study, Boston, Massachusetts.
authors.forename: Galit
authors.initials: G
authors.lastname: Weinstein
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts2The Framingham Heart Study, Boston, Massachusetts3Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Alexa S
authors.initials: AS
authors.lastname: Beiser
authors.affiliation: Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Seung Hoan
authors.initials: SH
authors.lastname: Choi
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts3Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Preis
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts.
authors.forename: Tai C
authors.initials: TC
authors.lastname: Chen
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts.
authors.forename: Demetrios
authors.initials: D
authors.lastname: Vorgas
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts2The Framingham Heart Study, Boston, Massachusetts.
authors.forename: Rhoda
authors.initials: R
authors.lastname: Au
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts2The Framingham Heart Study, Boston, Massachusetts.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Pikula
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts2The Framingham Heart Study, Boston, Massachusetts.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Wolf
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts2The Framingham Heart Study, Boston, Massachusetts3Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Anita L
authors.initials: AL
authors.lastname: DeStefano
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts2The Framingham Heart Study, Boston, Massachusetts.
authors.forename: Ramachandran S
authors.initials: RS
authors.lastname: Vasan
authors.affiliation: Department of Neurology, Boston University School of Medicine, Boston, Massachusetts2The Framingham Heart Study, Boston, Massachusetts.
authors.forename: Sudha
authors.initials: S
authors.lastname: Seshadri
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000097:blood* / Q000235:genetics / Q000517:prevention & control*; D019208:Brain-Derived Neurotrophic Factor / Q000097:blood* / Q000235:genetics; D003704:Dementia / Q000097:blood* / Q000235:genetics / Q000517:prevention & control*; D005260:Female; D005838:Genotype; D006801:Humans; D015994:Incidence; D008297:Male; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012306:Risk; D012680:Sensitivity and Specificity
chemical_list: D019208:Brain-Derived Neurotrophic Factor