We know that people with Alzheimer’s disease and other forms of dementia also suffer from depression. Some studies have shown that people with a history of major depression are twice as likely as others to eventually develop dementia. However, nobody really knows whether depression is a symptom of dementia or a potential cause of it.

Scientists from Rush University Medical Center tracked the symptoms of depression during the transition from no cognitive impairment and discovered that depressive symptoms showed little change during the development and progression of Alzheimer’s disease. You can read about this study in the July 6th edition of the peer-reviewed medical journal Neurology, an American Academy of Neurology publication.

Lead author Robert S. Wilson, PhD, senior neuropsychologist, Rush Alzheimer’s Disease Center, and a professor in the Department of Behavioral Sciences at Rush, said:

Our study suggests that depression is truly a risk factor for Alzheimer’s disease. If depression was an early sign of the disease, we would expect to see it increase prior to diagnosis and as the disease progresses. Our study found very little change. Depression should not be viewed as an inevitable part of Alzheimer’s disease. If a patient with Alzheimer’s has depression, the depression should be treated.

Study participants included individuals in the Chicago Health and Aging Project, a longitudinal study of risk factors for Alzheimer’s disease of older adults on Chicago’s south side. They all completed a self-report measure of depressive symptoms every three years; clinical evaluations for Alzheimer’s disease were also done.

They initially examined 357 people who had developed Alzheimer’s disease during the course of the study. The researchers detected a barely perceptible rise in depressive symptoms, a rate of 0.04 symptoms annually for a period of 6 to 7 years of monitoring before an Alzheimer’s disease diagnosis was made – and no change during the 2 to 3 years of observation after diagnosis.

The researchers conducted further analyses of change in depressive symptoms by interviewing family, friends and people who were close to the study participants, to make up for possible inaccuracies in self-reports by people with dementia. During the mean of 3 years of observation they found that neither Alzheimer’s disease nor its precursor (mild cognitive impairment) was linked with change in depressive symptoms.

The researchers report that the results were consistent across all demographics. Sex, age, education or race did not influence the trajectory of depressive symptoms before or after Alzheimer’s disease diagnosis

Wilson said:

Here is this terrible disease that robs people of who they are and their ability to function and yet it doesn’t make them depressed. Alzheimer’s may disrupt the ability to have prolonged bouts of negative emotions, in much the same way it disrupts many other activities.

The researchers say there should be further studies to see whether depressive symptoms may eventually decrease as Alzheimer’s disease severity worsens. They are currently looking at why depression raises the risk of Alzheimer’s disease.

The study was supported by funding from the National Institutes of Health (NIH)/ National Institute on Aging (NIA). Co-authors include G.M. Hoganson, BS; K.B. Rajan, PhD; L.L. Barnes, PhD; C.F. Mendes de Leon, PhD; and D.A. Evans, MD.

http://www.neurology.org/cgi/content/abstract/75/1/21“Temporal course of depressive symptoms during the development of Alzheimer disease”
R.S. Wilson, PhD, G.M. Hoganson, BS, K.B. Rajan, PhD, L.L. Barnes, PhD, C.F. Mendes de Leon, PhD and D.A. Evans, MD
NEUROLOGY 2010;75:21-26

Source: Rush University Medical Center

Written by Christian Nordqvist