title: The relationship between cholesterol and cognitive function is homocysteine-dependent.
abstract: BACKGROUND
  Previous studies have identified hyperlipidemia as a potential risk factor for dementia and Alzheimer's disease. However, studies on cholesterol measured in late-life and cognitive function have been inconsistent. Few studies have explored nonlinear relationships or considered interactions with other biomarker measures.
  
  
  METHODS
  A cross-sectional sample of 1,889 participants from four rural counties in the People's Republic of China was included in this analysis. Serum total cholesterol, high-density lipoprotein, triglycerides, and homocysteine levels were measured in fasting blood samples. A composite cognitive score was derived based on nine standardized cognitive test scores. Analysis of covariance models were used to investigate the association between biomarker measures and the composite cognitive scores.
  
  
  RESULTS
  There was a significant interaction between the homocysteine quartile group and the cholesterol quartile group on cognitive scores (P=0.0478). In participants with normal homocysteine levels, an inverse U-shaped relationship between total cholesterol level and cognitive score was found, indicating that both low and high cholesterol levels were associated with lower cognitive scores. In participants with high homocysteine levels, no significant association between cholesterol and cognition was found.
  
  
  CONCLUSIONS
  The relationship between cholesterol levels and cognitive function depends upon homocysteine levels, suggesting an interactive role between cholesterol and homocysteine on cognitive function in the elderly population. Additional research is required to confirm our findings in other populations, and to explore potential mechanisms underlying the lipid-homocysteine interaction.
authors.affiliation: Institute for Environmental Health and Related Product Safety, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
authors.forename: Yibin
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Institute for Environmental Health and Related Product Safety, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
authors.forename: Yinlong
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Department of Psychiatry, Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Unverzagt
authors.affiliation: Institute for Environmental Health and Related Product Safety, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
authors.forename: Liqin
authors.initials: L
authors.lastname: Su
authors.affiliation: Department of Biostatistics, Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Lili
authors.initials: L
authors.lastname: Yang
authors.affiliation: Institute for Environmental Health and Related Product Safety, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
authors.forename: Feng
authors.initials: F
authors.lastname: Ma
authors.affiliation: Department of Neurology, Indiana University School of Medicine, Indianapolis, Indiana, USA ; Eli Lilly and Company, Indianapolis, Indiana, USA.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Hake
authors.affiliation: Department of Biostatistics, Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Carla
authors.initials: C
authors.lastname: Kettler
authors.affiliation: Institute for Environmental Health and Related Product Safety, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.affiliation: Institute for Environmental Health and Related Product Safety, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
authors.forename: Jingyi
authors.initials: J
authors.lastname: Liu
authors.affiliation: Shandong Institute for Prevention and Treatment of Endemic Disease in China, Jinan, People's Republic of China.
authors.forename: Jianchao
authors.initials: J
authors.lastname: Bian
authors.affiliation: Sichuan Provincial Center for Disease Control and Prevention in China, Chengdu, People's Republic of China.
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.affiliation: Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Jill R
authors.initials: JR
authors.lastname: Murrell
authors.affiliation: Department of Psychiatry, Indiana University School of Medicine, Indianapolis, Indiana, USA ; Indiana University Center for Aging Research, Indianapolis, Indiana, USA ; Regenstrief Institute, Inc., Indianapolis, Indiana, USA.
authors.forename: Hugh C
authors.initials: HC
authors.lastname: Hendrie
authors.affiliation: Department of Biostatistics, Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Sujuan
authors.initials: S
authors.lastname: Gao
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000097:blood*; D002681:China; D002784:Cholesterol / Q000097:blood*; D003430:Cross-Sectional Studies; D003704:Dementia / Q000097:blood*; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood*; D008075:Lipoproteins, HDL / Q000097:blood; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011594:Psychometrics; D012307:Risk Factors; D013223:Statistics as Topic; D014280:Triglycerides / Q000097:blood
chemical_list: D008075:Lipoproteins, HDL; D014280:Triglycerides; D006710:Homocysteine; D002784:Cholesterol
keywords: cholesterol; cognitive function; homocysteine