Symptoms of depression late in life have been linked to an increased risk of Alzheimer's disease. But is depression a cause or an effect of the disease?
Researchers speculate that in some people, Alzheimer's could be a long process that begins many years before the actual onset of memory loss, showing up as symptoms of depression in the early stages of the disease. Alternatively, it is possible that depression may in some way damage the brain, making it vulnerable to the ravages of Alzheimer's.
In the current study, scientists at the University of Washington set out to clarify the relationship between depression and Alzheimer's by studying 3,410 seniors living in the Seattle area. At the start of the study, less than one in 10 of the participants had symptoms of depression. More than one in five had a history of depression earlier in their lives.
The men and women, aged 65 and older, were followed for an average of seven years. During that time, 658, or about 19 percent, developed Alzheimer's or another form of dementia.
Those who suffered from depression after age 50 were significantly more likely to develop Alzheimer's during the study period. The risk was increased even when the researchers considered age, years of schooling and other known risk factors for Alzheimer's.
Other research suggests that Alzheimer's is preceded by a period in which a person becomes concerned about memory loss and thinking problems. For example, people may respond "Yes" to questions like, "Do you think you move more slowly than you used to?," "Do you feel more exhausted than you used to?" and "Do you have problems concentrating?" Worry about failing memory can, understandably, make someone feel depressed.
This study sought to clarify whether symptoms of depression were an early sign of Alzheimer's. If people who were depressed at younger ages tended to develop Alzheimer's in old age, it would be a sign that depression is linked to the disease.
But in this study, a history of depression before age 50 did not increase the risk of developing Alzheimer's as a senior, suggesting that depression symptoms in later life may, for some people, be early signs of the disease. People who scored high on a test of depression as well as those who subjectively felt like they were slowing down were at increased risk of developing the disease.
Understanding the mechanisms linking depression with Alzheimer’s could suggest novel approaches to delay dementia onset. It is also important to recognize symptoms of depression since, unlike Alzheimer’s, it can be successfully treated. Up to half of patients with Alzheimer’s disease also have depression, which can take a serious toll on both patients and caregivers.
Symptoms of depression are many and varied. They include:
* Feeling sad, apathetic, or hopeless for weeks to months on end.
* Loss of interest in daily activities, especially ones that used to bring pleasure.
* Poor appetite and weight loss; or increased appetite and excessive weight gain.
* Troubled sleep, waking up repeatedly during the night, or an increased need for sleep.
* Feeling anxious or agitated.
* Trouble thinking or an inability to concentrate.
* Focusing on non-serious physical complaints.
If you experience one or more of these symptoms, or other unusual changes in mood or behavior, consult your physician. Medications and therapeutic counseling are available that can provide relief.
Source: Ge Li; Lucy Y. Wang; Jane B. Shofer; Mary Lou Thompson; et al: Temporal Relationship Between Depression and Dementia: Findings From a Large Community-Based 15-Year Follow-up Study. Archives of General Psychiatry. Sept. 2011; Vol. 68(9): pages 970-977.