Dementia: Update for the Practitioner

Depression can be diagnostically quite complicated. It has been noted in a number of Alzheimer's studies that the prevalence of major depression is higher in the caregiver than in the patient. When the caregiver says that the patient is depressed, the caregiver may be saying, "I am depressed." When assessing depression, you must question the caregiver's situation as well as the patient's situation. The patient may seem very calm and in good spirits, while the caregiver seems down and says that the patient is depressed. On the other hand, the patient may be clearly depressed and need treatment. This is obviously not the case when you're dealing with psychosis; if the caregiver says the patient is psychotic, it is extremely rare that the caregiver is psychotic.

Major depression in dementia occurs in inpatients from 10 to 40 percent across studies. The range has to do with how depression is defined and evaluated. There are a large number of symptoms which can occur in both depression and dementia: apathy, anhedonia, insomnia, agitation, memory loss, and difficulty concentrating. Assessment and making the right diagnosis are particularly important in this case.

In the multisite study I mentioned earlier, even though depressed mood was present in 15 to 20 percent of patients, depressed mood with insomnia and loss of appetite appeared in fewer than 5 percent. The classic major depressive syndrome is not common.


	Prevalence of Psychopathology During Three-Year Follow-up (n=236)


	The prevalence of psychopathology during three-year follow-up of 236 Alzheimer's patients. Courtesy of Dr. Davangere P. Devanand. Source of data: D. P. Devanand et al., "The Course of Psychopathologic Features in Mild to Moderate Alzheimer's Disease," Archives of General Psychiatry 54, no. 3 (March 1997): 257–63.

The infamous term pseudodementia refers to the idea that a patient may present with severe memory loss and cognitive deficits, and what seems to be dementia is actually depression. Pseudodementia was discussed frequently about twenty years ago, but it is an uncommon clinical presentation. Now that we have good follow-up studies on many of these patients, we know that cognitively impaired people with depression may go on to develop dementia.

Our ongoing epidemiologic study in north Manhattan found that, among people who had depressed mood at baseline on the Hamilton depression-rating scale, the likelihood of becoming demented over an average three-and-a-half year follow-up was three times higher than for those who did not have depressed mood at baseline. That study and subsequent studies do not suggest that depression is an independent risk factor, but rather a prodrome for dementia. In the early stages, as a person is developing memory loss and progressing towards dementia, depression is common, and that is what we have picked up in studies.


	Survival Curves for Depressed and Nondepressed Subjects


	Courtesy of Dr. Davangere P. Devanand. Source of data: D. P. Devanand et al., "Depressed Mood and the Incidence of Alzheimer's Disease in the Elderly Living in the Community," Archives of General Psychiatry 53, no. 2 (February 1996): 175–82.

In assessing a patient, consider whether there have been any previous personal or family depressive episodes, prior treatment response, and drug or alcohol use. In the elderly, alcohol is an issue, but other drugs rarely are. Corticosteroids, sedatives, benzodiazepines, and other drugs can not only cause some cognitive deficits but can also be associated with some depressive symptoms.

Other evaluation issues are similar to those in a general dementia work-up, including onset, duration, and progression. We generally like to think that if depression preceded cognitive deficits, the patient has depression, and if cognitive deficits preceded depression, the patient has dementia. In reality, it is very difficult to make this differential diagnosis. When we try to tease these things apart in patients and families we either cannot do it at all, or we get different answers from different family members of the same patient.

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