ST. PAUL, MN – Symptoms of depression may be one of the first signs of Alzheimer's disease, occurring up to three years before the disease is diagnosed, according to a study in the December 10 issue of Neurology, the scientific journal of the American Academy of Neurology.
The study followed 222 people age 74 and older in Stockholm, Sweden, over three years. The 34 people who developed Alzheimer's disease during that time were compared to the 188 people who did not develop the disease.
"The people who developed Alzheimer's weren't even close to a clinical diagnosis of depression, but they did have more symptoms of depression - such as a lack of interest, loss of energy and difficulty concentrating - at the beginning of the study than the rest of the participants," said study author Lars Bäckman, PhD, director of the Stockholm Gerontology Research Center.
In general, those who developed Alzheimer's were 50 percent more likely to have symptoms of depression than the other participants. One symptom, lack of interest, was three times more common in those who later developed Alzheimer's.
Researchers say the study shows that physicians and others who are assessing elderly people should consider depression symptoms in their evaluations.
"Treatment for Alzheimer's disease is becoming increasingly successful, and the treatment is most likely to succeed if it's given early in the course of the disease," Bäckman said. "Therefore, it's critically important to diagnose Alzheimer's as early as possible. Looking for these depression symptoms may be one way to identify who will develop Alzheimer's in a few years."
Researchers have known that people with Alzheimer's are more likely to experience depression, but they didn't know whether the depression was related to people's emotional response to growing memory problems and other cognitive difficulties. This study showed that the depression is not related to memory complaints.
Researchers also have questioned whether depression is an early sign of developing Alzheimer's disease or a risk factor for the disease, meaning that people who are depressed are more likely to later develop Alzheimer's. This study provides evidence that depression is an early sign of the disease, not a risk factor for the disease.
The study looked at two types of depression symptoms - mood-related symptoms and motivation-related symptoms. Mood-related symptoms include unhappiness, feelings of guilt and thoughts of death or suicide. Motivation-related symptoms include lack of interest, loss of energy and difficulty concentrating.
"The symptoms seen in the people who would later be diagnosed with Alzheimer's were mostly motivation-related," Bäckman said. "That provides further evidence that the symptoms are not related to people's feelings about their cognitive difficulties and actually reflect changes in the brain regions involved in attention and energy. Because these symptoms - lack of interest, loss of energy and difficulty concentrating - are fairly common in the normal older population, these symptoms may be easily overlooked as early signs of an emerging disease." The number of elderly people in the population is expected to grow in the years to come. "That will bring an increase in the number of people with Alzheimer's disease" Bäckman said. "The expected burden from this increase is immense on society and on caregivers. It's of critical importance to increase our knowledge of diagnosing the disease early."
The American Academy of Neurology, an association of more than 16,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research.
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Neurology