That high-stress job may be doing you more harm than you thought.
For the first time, researchers have shown direct evidence that prolonged exposure to stress can accelerate the aging of brain cells and lead to impairment of learning and memory.
In the studies, stress caused rats to produce abnormally high levels of stress hormones, such as adrenalin, which damaged brain cells, a Kentucky researcher reported yesterday in the Journal of Neuroscience.
In older rats, the stress led directly to the death of brain cells, a finding that may shed light on the cause of Alzheimer's disease -- which already has been correlated with high levels of the hormones.
The new study "represents an important advance in research on biomarkers of brain aging and may ultimately point the way to interventions that will prevent [deterioration of mental processes] in older people," said neurologist T. Franklin Williams, director of the National Institute on Aging, who is familiar with the new study.
"In my judgment, the discovery plays a key role in tying together many disparate observations from different laboratories that study aging," said neurobiologist Zevan Khachaturian, also of the institute on aging. Research on the stress hormones, he said, "is getting more and more exciting."
The results are important because the region of the brain that the researchers studied is the hippocampus, the same region that is severely damaged in humans suffering from Alzheimer's, a devastating progressive disorder that affects at least 2 million Americans, most of them over the age of 65.
Damage to the hippocampus in Alzheimer's victims first causes subtle memory loss, problems using language and spatial disorientation. When the damage becomes more severe, it causes marked memory loss and impaired thought processes, and often leads to incapacitation and death.
The new results suggest that stress makes brain cells in the hippocampus -- which is important to both learning and memory -- work harder and thus leaves them more vulnerable to damage from other causes, in much the same way that fatigue and exhaustion can render an individual more susceptible to colds and flu, Khachaturian said. The ultimate damage to hippocampal cells might then be caused by a short interruption of blood flow to the brain, low blood-sugar levels, chemicals in the environment or even chemicals produced by the brain, the researchers said.