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Temporal Relation Between Depression and Cognitive Impairment in Elderly

This study clarifies that depression follows rather than leads to dementia.

These researchers examined the temporal relation between depression and cognitive decline over a 4-year period in 500 elderly (85 years old at recruitment) inhabitants of Leiden, the Netherlands. At baseline, participants had a mini-mental state examination (MMSE) score of 19 points or more. Annual assessments included the geriatric depression scale (GDS), MMSE, attention test (STROOP), processing-speed test, and immediate- and delayed-recall tests (based on a 12-word learning test).

Depression (GDS score >2) and cognitive impairments co-occurred. Whereas depression correlated significantly with lower scores on the MMSE, depression at baseline was not associated with subsequent accelerated cognitive decline. In contrast, impairments of attention and memory preceded the development of depressive symptoms. Thus, the findings supported previous research showing that depression was not a risk factor for Alzheimer disease (AD), but rather was a primary sign of AD (Arch Gen Psychiatry 1999; 56:261). The authors of the current study speculate that an elderly person's awareness of his or her cognitive decline can cause depression. They conclude that caregivers should watch for depression in patients with cognitive impairment.

Comment: This well-designed study with rigorous follow-up was strengthened by the use of the "mixed models" design in the statistical analysis. Recent, less rigorous studies on this subject showed conflicting results. Some suggested that depression is a risk factor for AD (Int J Geriatr Psychiatry 2002; 17:997; Arch Gen Psychiatry 1996; 53:175; and Br J Psychiatry 2002; 181:406). Others showed no clear relation between depression and the sorts of changes in hippocampal structure and function common in memory disorders (e.g., Biol Psychiatry 2004; 56:101). In contrast, the bidirectionality of the current study allowed ascertainment of a temporal relation (i.e., co-occurrence) but no causal association (i.e., depression did not lead to cognitive decline). As the authors suggest, it is important to screen for depression in the elderly. Quality-of-life assessment and companions' interviews, which were not used in this study, might have aided the diagnosis and characterization of depression. Additional research is needed to elucidate this association further.

— Zeina Chemali, MD

Dr. Chemali is Director, Neuropsychiatry, Brigham Behavioral Neurology Group, Brigham and Women's Hospital, Boston.

Published in Journal Watch Neurology January 14, 2005

Citation(s):

Vinkers DJ et al. Temporal relation between depression and cognitive impairment in old age: Prospective population based study. BMJ 2004 Oct 16; 329:881.

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