One of the largest and longest studies to date shows that being depressed increases the risk of developing Alzheimer’s or other forms of dementia later in life by 50 percent.
The study, part of the large and ongoing Framingham Heart Study, followed 949 men and women over 17 years. All were free of serious memory problems at the start. Participants were also surveyed about feeling sad or hopeless, trouble sleeping, poor social relationships and other signs and symptoms of depression; 125, or 13 percent, had depression at the start of the study.
At the end of the study, 136 of the participants had been diagnosed with Alzheimer’s disease; another 28 had other forms of dementia. Nearly 22 percent of people who were depressed at the start of the study had developed Alzheimer’s or another type of dementia, compared to only about 17 percent of those who were not depressed. Researchers controlled for factors like age, sex, level of education or carrying the APOE-E4 gene, which can increase the risk of Alzheimer’s, and determined that Alzheimer’s risk was nearly twice that for depressed people than those who were not depressed.
“While it’s unclear if depression causes dementia, there are a number of ways depression might impact the risk of dementia,” said study author Jane Saczynski, Ph.D., of the University of Massachusetts Medical School in Worcester. “Inflammation of brain tissue that occurs when a person is depressed might contribute to dementia. Certain proteins found in the brain that increase with depression may also increase the risk of developing dementia. In addition, several lifestyle factors related to long-term depression, such as diet and the amount of exercise and social time a person engages in, could also affect whether they develop dementia.”
The fear and anxiety that accompanies a diagnosis of Alzheimer's disease can understandably cause patients to become depressed. But the results of this study, published in the journal Neurology, add to a growing body of evidence that suggests that a pattern of depression, even decades earlier, ups the risk for developing Alzheimer's.
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. Alternatively, it is possible that depression may in some way prove "toxic" to the brain.
A study from 2008, for example, found that a history of depression, particularly before age 60, increases the risk for Alzheimer’s. Unlike in the current study, however, those with depressive symptoms at the study start were not more likely to develop Alzheimer’s later, though the study only lasted six years.
Understanding the mechanisms linking depression with Alzheimer’s could suggest novel approaches to delay dementia onset. It’s 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 and may 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: J.S. Saczynski, A. Beiser, S. Seshadri, S. Auerbach, P.A. Wolf, and R. Au: "Depressive symptoms and risk of dementia: The Framingham Heart Study." Neurology, Vol. 75, page 35, July 6, 2010.