Moodiness, loss of energy, indifference toward others, withdrawing from social activities—these may not sound like symptoms of Alzheimer's disease (AD), but a study published in January in the journal Neurology suggests that these signs of depression may actually be harbingers of AD.
Over the course of seven years, the study looked at 2,416 adults over age 50 who had normal cognition. During that time, study leader Catherine M. Roe, PhD, a research assistant professor of neurology in the Charles F. and Joanna Knight Alzheimer's Disease Research Center at Washington University School of Medicine in St. Louis, MO, and a member of the American Academy of Neurology (AAN), and colleagues administered psychiatric tests to look for changes in behavior such as depression, hallucinations, aggression, anxiety, and differences in sleep and eating habits.
Many of the participants later developed dementia. And while many of the older adults—not just those who progressed to dementia—began to exhibit more of the above behavioral problems over time, those who developed dementia showed signs of these depression-related traits years earlier than those who did not.
MOOD MAY GO BEFORE MEMORY
“When you think of Alzheimer's disease, you think of problems with memory being a very early symptom,” says Dr. Roe. “But in this case, low energy appeared first, followed by a tendency to stay at home.” She adds that although these older adults were experiencing some features of depression, very few were clinically depressed or needed antidepressants during this study.
“Dropping activities and interests, being more likely to stay at home than to go out and do things, and lack of energy were the three depressive features that were more likely to develop in people who were later diagnosed with early dementia,” says study author John C. Morris, MD, director of the Knight Alzheimer's Disease Research Center at Washington University in St. Louis, a Fellow of the AAN, and a member of the Neurology Now editorial advisory board. The appearance of these symptoms later in life “could be a warning sign” for subsequent dementia, he says.
THE DEMENTIA-DEPRESSION LINK
Research has not proven that people with depression are more likely to develop dementia, but many studies have found a link between the two conditions.
In a paper published in 2013 in the British Journal of Psychiatry, for instance, researchers reviewed 23 studies of nearly 50,000 adults over age 50 and found that those with depression were 65 percent more likely to develop AD and more than twice as likely to develop vascular dementia—cognitive decline caused by conditions that block or reduce blood flow to the brain—as adults who weren't depressed.
“There may be an underlying biologic or genetic connection between the two conditions,” says Dr. Morris. For example, an April 2010 study published in the journal Psychoneuroendocrinology found that people who experience depressive traits such as feelings of hopelessness and loneliness have higher levels of the stress hormone cortisol, which can damage the hippocampus, a part of the brain involved in learning, mood, and memory that becomes impaired early in AD.
ANTIDEPRESSANTS AND DEMENTIA
Research is underway to see whether taking antidepressants can lower the risk for developing AD.
One such study, led by Yvette Sheline, MD, a professor of psychiatry at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, and published in the journal Science Translational Medicine in 2014, looked at whether people taking the antidepressant citalopram (Celexa) would have lower levels of the protein amyloid-beta (which forms toxic “plaques” in the brains of people with AD) in their cerebrospinal fluid than people who were not taking the drug.
Indeed, researchers found that amyloid-beta production slowed by 37 percent in the brains of people taking citalopram compared with those on placebo therapy. This change led to a 38 percent total decrease in the amount of amyloid-beta in the brain.
Dr. Sheline and colleagues are now doing a longer-term study of antidepressants and AD and hope the outcome will be much the same. If it is, Dr. Sheline says, “it might provide a prophylactic option to prevent AD.”
5 Ways to Diminish Your Risk of Dementia
1. Eat a heart-healthy diet
2. Manage medical conditions
3. Stay mentally and physically active
4. Remain socially engaged
5. Don't ignore depression
WEB EXTRA: Find out more about these tips at http://bit.ly/NN-dementia-risk.