Is It Late Life Depression or Dementia? 7/6/2017

It is often difficult to differentiate between depression and dementia in older patients, particularly because there is overlap in the presenting symptoms and the two disorders can occur co-morbidly. Population studies have shown that over the age of 85, the two disorders occur co-morbidly in 1 out of 4 people. And late-life depression is a risk factor for the development of Alzheimer’s dementia and other forms of dementia. Studies have shown that depression onset later in life is either a prodromal symptom of dementia or increases the susceptibility of dementia later in life. When a patient has cognitive impairment as part of their presentation of late-life depression, it often persists even when the mood symptoms resolve and can lead over time to a more serious dementia.

For a patient with late-life depression, it can be difficult to determine if the associated cognitive impairments are directly related to the depression versus representative of early dementia. There are some key differences that can be assessed for clinically. It is important to assess for changes ability to manage daily activities and decrease in community involvement and determine if those changes are related to loss of knowledge or ability (seen in Alzheimer disease) or loss of interest or motivation (seen in depression and some causes of dementia).

Common cognitive deficits that can occur in late-life depression include: problems with information processing speed (slow to respond or initiate behavior, incomplete grasp of complex information), inattention and poor concentration (absentmindedness for daily activities), problems with memory, and challenges with executive functioning (planning, organizing, multitasking). These are more specific deficits as compared to the more general and universal deficits seen in dementia and can be helpful in differentiating the two.

It is of course also important to assess for other non-cognitive symptoms of depression to help determine which diagnosis is more appropriate. These are discussed in more detail in a previous e-Weekly. Collateral from family members can be especially helpful for information about onset of symptoms, changes in personality, and ability to engage in activities of daily living. Frequently a careful assessment of family history can be helpful to determine if there is a history in the family of depression and other mood disorders and of dementia. If there is a family history of dementia, it is important to ask about age of onset.

It is also common to see symptoms of depression in patients with dementia. Studies show between 10-30% of patients with mild-moderate Alzheimer’s dementia also meet criteria for a major depressive episode. Higher rates of depression are seen in patients with vascular dementia.

The table on page 2 is included to show the similarities and differences and overlaps between depression and dementia in late-life. It is our hope that it is helpful clinically with older patients.


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