A study released in March by the University of California, San Diego School of Medicine appears to back up earlier hypotheses that link stress with Alzheimer's. But not all types of stress are to blame.
Acute stress, caused by a sudden, single event such as an accident, is not implicated in the study, which was published in Proceedings of the National Academy of Sciences. It is chronic stress — the ongoing, unrelenting stress you might experience in, say, a difficult job or living situation — that's the culprit.
How the Test Was Done
In the study, mice were placed in vented plastic tubes for 30 minutes a day over a two-week period. While inside the tubes, they were denied access to food and water. Rissman notes that the effect of restraining the mice has been found in endocrinological studies to be “roughly equivalent to the … stress experienced by humans” during prolonged periods of emotional strain.
"This isn’t an exact science," he adds, "but the data look pretty convincing.”
Previous studies have also shown a strong connection between stress and Alzheimer’s. In one conducted at the Max Planck Institute of Psychiatry in Munich, which was published in the Journal of Neuroscience in May 2011, persistent stress in rats led to a similar result: the formation of clumps in the brain and, ultimately, memory loss.
But what's significant about the UC San Diego study, Rissman says, is that earlier studies showing the connection between stress and the protein clumps usually involved mice with rare genetic mutations that promoted the pathology. “Here we haven’t used any mutations at all to get our phenotype … just exposure to emotional stress,’’ he says.
Alzheimer's Expected to Soar
Estimates of the number of Americans afflicted by Alzheimer’s range from 5.1 million to 5.4 million, and someone develops the disease every 68 seconds, according to the Alzheimer’s Association. Absent a cure, that figure is expected to climb as high as 16 million by 2050 as baby boomers age.
Chronic Stress: Too Much of a Good Thing?
Rissman acknowledges that a certain amount of stress is inevitable in life and may even be healthy.
Especially as we age.
The Effects of Job-Related Stress
In this case, a group of researchers, many of them from Stockholm University, followed 913 people 75 and older over a six-year period to look at the long-term effect of job-related stress. Their finding: Continuous emotional stress experienced by those with low job control and high job strain was associated with an increased risk of dementia and Alzheimer's.
The Good New for Researchers
All of this is good news for researchers: The findings pave the way toward exciting new research possibilities aimed at preventing or delaying the disease. But making such strides will take time, Rissman says. “I would hope that we could get the necessary [research] done within the next five years.’’
There may be benefits in changing jobs, seeking counseling, exercising, meditating or taking other measures to alleviate chronic stress. But Rissman has another long-term goal: to develop a way to reduce the effects of stress on neurons, so it doesn’t result in permanent damage.