A 'silent' cause of depression in the elderly

Summarized by Robert W. Griffith, MD
March 30, 2000 (Reviewed: November 11, 2002)

Depression is not uncommon in older persons, and it usually responds to appropriate medical treatment. Not all cases of depression, however, are purely "psychiatric" in origin. As an example, a recent study in a large number of volunteers has shown that symptoms of depression can be linked to changes seen on magnetic resonance imaging (MRI) of the brain.

The Cardiovascular Health Study examines people over 65 selected from Medicare lists living in 4 areas of the USA - Pennsylvania, Maryland, California and North Carolina. In 1990 over 3,500 volunteers were enrolled who were prepared to have brain MRI scans after 4, 5 and 6 years in the study. At the outset they were given a short questionnaire to complete that asked about their mood, energy, irritability, concentration and any sleep difficulties. Other questionnaires asked about activities of daily living (such as self-care) and more complex living activities (e.g. using the phone, going shopping). A test of mental ability was also included, along with blood pressure measurements and a careful history of any cardiovascular disease.

The MRIs were read by specialists who looked for areas of change suggestive of loss of blood supply. Their findings were compared with the results of the questions on depressive symptoms.

Depressive symptoms were slightly more common in older people, women, nonwhite, those with high blood pressure, heart disease and some disabilities. This meant that it was necessary to correct for these factors in looking for possible relationships between depressive symptoms and MRI findings.

The amount of depressive symptoms was found to increase as the presence of small areas of damage in an area of the brain called the basal ganglia increased. This area, deep within the brain, acts as a relay station between different parts of the brain, including the cortex, where information is processed. The small lesions seen on MRI could represent a breakdown in the connection between the basal ganglia and the cortex, according to the principal author of the study. The change is suggestive of blockage of a small artery by a clot, in other words, a stroke on a small scale. The presence of these small blockages was clearly related to the degree of depressive symptoms reported - the greater the number of lesions, the worse the depressive symptoms. Such lesions are called "silent strokes" because they are not accompanied by the classic signs of stroke, such as severe headache, dizziness or paralysis.

The basal ganglia area is also involved in the regulation of movements. It is possible that small lesions occurring here might be responsible for some of the reduction in physical activity often seen in depressed patients.

The findings of this study suggest that in some patients with depression, changes may have occurred in the blood vessels of the brain that can predict a full-blown stroke or one type of dementia - vascular dementia. This means that physicians caring for elder patients with depression should be on the lookout for other risk factors for stroke or vascular dementia - high blood pressure, high blood sugar levels, high cholesterol levels, smoking, and physical inactivity. If these are recognized and corrected by appropriate medication and changes in lifestyle, the chances of the patient having a stroke will be reduced.

Source

• Cerebrovascular disease and depression symptoms in the Cardiovascular Health Study. DC. Steffens, MJ. Helms, K. Krishnan, GL. Burke, Stroke, 1999, vol. 30, pp. 2159--2166

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