A study has pointed out that symptoms of depression does not change much during the development and progression of Alzheimer's disease.
Researchers at Rush University Medical Center tracked symptoms of depression during the transition from no cognitive impairment to dementia and found that depression is a risk factor and not an early sign of Alzheimer's disease.
"Our study suggests that depression is truly a risk factor for Alzheimer's disease," said lead author Dr. Robert S. Wilson.
"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," he added.
The study involved participants in the Chicago Health and Aging Project, a longitudinal study of risk factors for Alzheimer's disease involving a population of older adults on Chicago's south side.
At three-year intervals, the entire population completed a brief self-report measure of depressive symptoms and clinical evaluations for Alzheimer's disease.
Initial analyses focused on a group of 357 individuals who developed Alzheimer's disease during the course of the study.
The study found a barely perceptible increase in depressive symptoms, a rate of 0.04 symptoms per year, during six to seven years of observation before the diagnosis of Alzheimer's disease and no change during two to three years of observation after the diagnosis.
Researchers conducted additional analyses of change in depressive symptoms by interviewing family, friends and other who were close to the study participants.
They found that neither Alzheimer's disease nor its precursor, mild cognitive impairment, was associated with change in depressive symptoms during a mean of three years of observation.
The results were consistent across all demographics. There was no evidence that sex, age, education or race modified the trajectory of depressive symptoms before or after Alzheimer's disease was diagnosed.
"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," said Wilson.
The study is published in the latest issue of Neurology.