title: Spectroscopic markers of memory impairment, symptom severity and age of onset in older people with lifetime depression: Discrete roles of N-acetyl aspartate and glutamate.
abstract: BACKGROUND
  Glutamate (Glu) and N-acetyl aspartate (NAA) are markers of excitatory processes and neuronal compromise respectively. Increased Glu and decreased NAA concentrations have been implicated in the pathophysiology of depression and cognitive impairment respectively.
  
  
  OBJECTIVE
  To determine the relationship between NAA, Glu, memory and key clinical features in older people with lifetime depression compared to comparison subjects.
  
  
  METHODS
  Thirty-five health-seeking older adults (mean age=63.57 years), with a lifetime depression diagnosis, and 21 age-matched healthy comparison subjects (mean age=65.48 years) underwent neuropsychological testing, psychiatric assessment and proton magnetic resonance spectroscopy from which Glu and NAA were measured (reported as a ratio to creatine).
  
  
  RESULTS
  Compared to comparison subjects, the depressed subjects showed poorer verbal learning and memory retention. Hippocampal NAA and Glu did not differ significantly between groups. However, in comparison subjects, lower levels of hippocampal Glu were associated with poorer memory retention (r=0.55, p=0.018). In the depressed subjects, lower levels of hippocampal NAA were related to poorer verbal learning (r=0.44, p=0.008) and memory retention (r=0.41, p=0.018). Greater hippocampal Glu was associated with more severe depressive symptoms (r=0.35, p=0.039) and an earlier age of illness onset (r=-0.37, p=0.031).
  
  
  CONCLUSIONS
  This is a cross sectional study with a heterogeneous group of depressed subjects.
  
  
  CONCLUSIONS
  Our findings highlight that hippocampal neurometabolites are entwined with both clinical and cognitive features associated with depression in older adults and further suggest that differential mechanisms may underpin these features.
authors.affiliation: Healthy Brain Ageing Program, Brain & Mind Research Institute, University of Sydney NSW Australia; Clinical Research Unit, Brain & Mind Research Institute, University of Sydney NSW Australia.
authors.forename: Hirosha K
authors.initials: HK
authors.lastname: Jayaweera
authors.affiliation: Clinical Research Unit, Brain & Mind Research Institute, University of Sydney NSW Australia.
authors.forename: Jim
authors.initials: J
authors.lastname: Lagopoulos
authors.affiliation: Healthy Brain Ageing Program, Brain & Mind Research Institute, University of Sydney NSW Australia; Clinical Research Unit, Brain & Mind Research Institute, University of Sydney NSW Australia; School of Psychology, University of Sydney NSW Australia.
authors.forename: Shantel L
authors.initials: SL
authors.lastname: Duffy
authors.affiliation: Healthy Brain Ageing Program, Brain & Mind Research Institute, University of Sydney NSW Australia; Clinical Research Unit, Brain & Mind Research Institute, University of Sydney NSW Australia.
authors.forename: Simon J G
authors.initials: SJ
authors.lastname: Lewis
authors.affiliation: Clinical Research Unit, Brain & Mind Research Institute, University of Sydney NSW Australia.
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Hermens
authors.affiliation: Healthy Brain Ageing Program, Brain & Mind Research Institute, University of Sydney NSW Australia; Clinical Research Unit, Brain & Mind Research Institute, University of Sydney NSW Australia.
authors.forename: Louisa
authors.initials: L
authors.lastname: Norrie
authors.affiliation: Healthy Brain Ageing Program, Brain & Mind Research Institute, University of Sydney NSW Australia; Clinical Research Unit, Brain & Mind Research Institute, University of Sydney NSW Australia.
authors.forename: Ian B
authors.initials: IB
authors.lastname: Hickie
authors.affiliation: Healthy Brain Ageing Program, Brain & Mind Research Institute, University of Sydney NSW Australia; Clinical Research Unit, Brain & Mind Research Institute, University of Sydney NSW Australia; School of Psychology, University of Sydney NSW Australia. Electronic address: sharon.naismith@sydney.edu.au.
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Naismith
mesh_terms: D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D003863:Depression / Q000175:diagnosis / Q000378:metabolism*; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis / Q000378:metabolism*; D008875:Middle Aged; D009483:Neuropsychological Tests; D017397:Prefrontal Cortex / Q000378:metabolism*
chemical_list: D001224:Aspartic Acid; D018698:Glutamic Acid; C000179:N-acetylaspartate
keywords: Depression; Glutamate; Magnetic resonance spectroscopy; Memory impairment; N-acetyl aspartate