By Maureen Salamon
WEDNESDAY, Jan. 14, 2015 (HealthDay News) -- Depression, sleep problems and behavioral changes can show up before signs of memory loss in people who go on to develop Alzheimer's disease, a new study suggests.
"I wouldn't worry at this point if you're feeling anxious, depressed or tired that you have underlying Alzheimer's, because in most cases it has nothing to do with an underlying Alzheimer's process," said study author Catherine Roe, an assistant professor of neurology at Washington University School of Medicine in St. Louis.
"We're just trying to get a better idea of what Alzheimer's looks like before people are even diagnosed with dementia," Roe added. "We're becoming more interested in symptoms occurring with Alzheimer's, but not what people typically think of."
Tracking more than 2,400 middle-aged people for up to seven years, the researchers found that those who developed dementia were more than twice as likely to be diagnosed with depression sooner than those without dementia.
Other behavior and mood symptoms such as apathy, anxiety, appetite changes and irritability also arrived sooner in participants who went on to cope with typical dementia symptoms, according to the research, published online Jan. 14 in the journal Neurology.
More than 5 million Americans are currently affected by Alzheimer's disease, a progressive, fatal illness causing not just memory loss but changes in personality, reasoning and judgment. About 500,000 people die each year from the incurable condition, which accounts for most cases of dementia, according to the Alzheimer's Association.
Roe and her team examined data from participants aged 50 and older who had no memory or thinking problems at their first visit to one of 34 Alzheimer's disease centers around the United States.
Over a period of up to seven years, about half remained cognitively normal, while the other half developed memory loss or thinking problems indicative of dementia.
Among the other findings, 30 percent of those who went on to develop dementia had depression after four years in the study, compared to 15 percent of participants who didn't have dementia.
Roe noted that research hasn't yet determined whether depression or other mood and behavioral changes result from the same underlying changes in the brain contributing to Alzheimer's disease, or as a psychological response to dealing with the condition. And while the study showed an association between behavioral changes and Alzheimer's risk, it did not prove a cause-and-effect link.
Keith Fargo, director of scientific programs and outreach for the Alzheimer's Association, praised the study, saying it offers a "fuller view of what might be happening with people who are developing dementia and people who are not.
"What people need to know about Alzheimer's is that it's not just problems with thinking and memory," he said. "It's a universally fatal brain disease where you lose the cells in your brain over time and that manifests in many different ways. One way is through dementia, but it can manifest in other ways such as depression, anxiety or trouble sleeping."
Fargo urged anyone who's noticing significant behavioral or mood changes in themselves or a loved one to speak to a physician.
"Don't try to tough it out and don't try to wait for it to go away," he said. "Those things are probably manageable through either lifestyle measures or medication, or they may be indicative of something larger going on such as dementia or Alzheimer's."