Background: Depression and high total plasma homocysteine (tHcy) are independently associated with cognitive impairment in older adults. We designed this study to determine if high tHcy is a mediator of cognitive performance in older adults with major depression.
Methods: We recruited 358 community-dwelling older adults experiencing depressive symptoms, 236 (65.9%) of who met DSM-IV-TR criteria for major depression. Assessment included the Montgomery Asberg Depression Rating Scale (MADRS), fasting tHcy and the Consortium to Establish a Registry for Alzheimer's Disease neuropsychological battery.
Results: Individuals with major depression and high tHcy had significantly worse immediate verbal and delayed visual recall. Non-depressed participants with high tHcy had lower MMSE, immediate and delayed recall scores than those with normal tHcy. The odds of cognitive inefficiency for those with high tHcy was nearly doubled for the MMSE (OR 1.9, 95%CI 1.1-3.3), immediate (OR 1.9, 95%CI 1.1-3.5) and delayed (OR 1.9, 95%CI 1.1-3.4) word recall after adjusting for age, gender, IHD and MADRS score.
Limitations: The presence of sub-syndromal depressive symptoms in our non-depressed group and exclusion of participants with established cognitive impairment may limit the generalizability of this study.
Conclusions: Elevated tHcy was associated with weaker performance in tests of immediate and delayed memory and global cognitive performance when compared to those with normal tHcy independent of the presence of major depression or the severity of depressive symptoms. Homocysteine lowering B-vitamin supplementation may offer a potential therapeutic target to try and mitigate the often-disabling impact of cognitive deficits found in this population.
Keywords: Cognition; Depression; Homocysteine.
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