Dementia is not a disease. It is a set of symptoms that might include varying degrees of memory loss, language difficulty, poor judgment, inability to concentrate, and impaired visual perception. Generally dementia is said to be present if two or more of these symptoms are present and severe enough to impair performance of everyday activities. “Dementia has many causes,” says Dr. Kenneth Freundlich, clinical neuropsychologist with The Morris Psychological Group. “Some dementias are treatable – for example, those caused by substance abuse, metabolic disorders and tumors. But the most prevalent dementias, those caused by Alzheimer’s disease and inadequate blood flow to the brain – known as vascular dementia – are generally progressive and incurable. As research on causes and prevention continues, we also continue to develop new strategies to reduce risk factors for dementia, to delay its onset and to slow its progression. New research published in May in the British Journal of Psychiatry (http://bjp.rcpsych.org/content/202/5/329.abstract) into the association between depression and dementia opens new lines of inquiry and helps us develop new coping strategies for patients and their families.”
About Depression and Dementia
There are currently more than 5 million people in the United States suffering from Alzheimer’s disease, the most common of the dementias, which accounts for 50-60% of cases. Vascular dementia, which is generally considered the second most common form, accounts for 20-30% of cases. Dementia is seen most often in the elderly. About 5% to 8% of all people over the age of 65 have some form of dementia, a number that doubles every five years after that age. As the population aged 65 and older continues to increase, the number of people with dementia will increase as well. “This population also exhibits symptoms of depression at higher rates than younger people,” says Dr. Freundlich. “Various estimates put the rate of depression in the elderly between 5% and 15%. An important new study confirms what has been suspected for some time – that there is an association between depression and Alzheimer’s. It also shows an even stronger relationship between depression and vascular dementia.”
Depression and Dementia Study Results:
The recent study analyzed 23 previous studies that followed nearly 50,000 older adults for a median period of five years. The researchers found that those with late-life depression were more than twice as likely to develop vascular dementia as those who were not depressed and that the risk of vascular dementia was even greater than the risk of Alzheimer’s for the depressed elderly. Interpretation of the data suggests that 72% of adults with late-life depression will go on to develop vascular dementia and 62% will eventually develop Alzheimer’s disease.
Alzheimer’s disease and vascular dementia result from different changes in the brain. Alzheimer’s is caused by the development of amyloid protein plaques outside brain cells and of tangles of a different protein inside the cells, causing damage first to the cortex of the brain—the area associated with learning, memory and language – then spreading to other parts of the brain. Vascular dementia is caused by reduced blood flow to the brain. When the supply of oxygen and nutrients is interrupted for longer than a few seconds, brain cells can die, also usually those in the cortex. The most common trigger for vascular dementia is a stroke or series of strokes, often the mini-strokes known as transient ischemic attacks (TIAs) that may go undetected but cause damage that adds up over time. Vascular dementia may come on gradually or suddenly, depending on the number and severity of the strokes.
There is as yet no evidence of a causal relationship between depression and dementia. Researchers are continuing to investigate both the biological and emotional underpinnings of both to better understand the linkage. For example, people with depression produce higher levels of the hormone cortisol, which is known to affect the part of the brain that controls new learning and short-term memory. Other studies have shown that depression may contribute to an inflammatory response that damages blood vessels. While it is possible that depression is a sign of incipient dementia and may be a contributing factor, it is also possible that depression is an emotional reaction to rather than a cause of the cognitive changes that signal the early stages of dementia.
Evaluate and treat
“Whatever the causative factors, depression and dementia are enormously burdensome for patients and their caregivers,” says Dr. Freundlich. “Seniors with signs of depression should be evaluated and treated aggressively with the appropriate combination of medication and psychotherapy. We can’t be certain that successfully treating depression will prevent the development of dementia but we can be confident that it will improve the quality of life and overall health in the elderly.”
