Late-life Depression Linked to Dementia
There is a recognized clinical problem in the assessment of depression in the elderly, mainly because the symptoms of early dementia (e.g. Alzheimer’s) appear so similar. Equally, there is always the possibility that symptoms of depression happen to coincide with those of dementia.
Vigilant clinicians may distinguish the two by observing specific symptoms and then of course there is the response to treatment. For example, depression in Alzheimer’s tends to be less severe, there is less talk of suicide and there is an increased risk of delusional talk or possibly hallucinations. In terms of treatment, antidepressants may have the effect of lifting mood in a relatively short period of time. But with dementia, which is a progressive degenerative disease, no such effects will be seen.
The exact relationship between depression and dementia isn’t fully understood, but the link is established. A major report, published in the British Journal of Psychiatry this year, disclosed that for every 50 older adults with late-life depression, 36 will go on to develop vascular dementia. The findings followed an analysis of 50,000 older adults over an average of five years.
The causal link is less certain. People with depression have elevated levels of cortisol, known to have adverse effects on certain areas of the brain associated with dementia. But depression also contributes to chronic inflammation and this can damage blood vessels leading to reduced blood flow and subsequent destruction of neural networks. So whether depression is an early sign of dementia or something that brings dementia to light earlier because of its physical effects, isn’t known.
Mild cognitive impairment is defined by the Mayo Clinic as, “an intermediate stage between the expected cognitive decline of normal aging and the more serious decline of dementia.” Perhaps not surprisingly, recent research also points to an association between depression and mild cognitive impairment. Depressive symptoms have been reported anywhere from 3 to 63 percent of patients with mild cognitive impairment, which according to study author Dr. Edo Richard, of the University of Amsterdam in the Netherlands, increases the risk of dementia.
Whether the identification and treatment of late-life depression could contribute to a reduction in dementia numbers is yet to be assessed. Dr. Deborah Barnes, contributing to Judith Graham’s article in the New York Times, suggests that almost 15 percent of Alzheimer’s cases are “potentially attributable to depression” and that a 10 percent reduction in depression could reduce dementia cases by as many as 68,000.