Scientists are closing in on identifying why some people who are under chronic stress -- such as those caring for someone who has Alzheimer's disease -- are particularly vulnerable to ill health while others in the same situation are not: their bodies can't produce enough white blood cells (called lymphocytes) to patrol the body fighting off challenges from outside.
Paul J. Mills, Ph.D., of the University of California at San Diego, and colleagues at UCSD and the Veterans Administration, found this when they stress-tested 20 elderly persons who care for relatives with Alzheimer's.
From a group of 41 spousal caregivers, they classified as vulnerable 10 who were required to provide care for their spouse more than 12 hours a day, every day, and who received a break from that routine less than once a month. Of the other 31 caregivers identified as "nonvulnerable," 10 were matched with the vulnerable caregivers on age and gender and served as controls.
All caregivers were given two speaking tasks back-to-back: to defend themselves from a false accusation that they had shoplifted, and to describe the most difficult caregiving situation they had encountered in the previous two weeks. Blood was collected before and after the tasks.
As the researchers report in the March issue of Psychosomatic Medicine, when at rest the vulnerable caregivers had on average only 40 percent as many circulating lymphocytes of two critical types as the caregivers who weren't vulnerable. These special memory T lymphocytes were identified by expression of surface adhesion molecules that support routine immune surveillance throughout the body.
This deficit was maintained after exposure to the acute psychological stress of the speaking tasks, suggesting that the vulnerable caregivers were unable to mount lymphocyte production adequate to overcome the deficit they-' had at rest.
"Acute stressors activate the sympathetic nervous system causing substantial lymphocytosis (a release of lymphocytes into the circulation)," the researchers explain. "Functional immune studies indicate that both acute and chronic stress lead to a reduction in T-lymphocyte-mediated immunity."
The researchers also found that the level of a stress hormone, catecholamine adrenaline (epinephrine), in the blood of the vulnerable caregivers was almost double that of the non-vulnerable.
They cite earlier studies that showed chronically stressed caregivers are more likely to develop hypertension and more likely to be hospitalized. In the current study, the vulnerable caregivers reported poorer overall health and that their illnesses lasted three times longer than was reported by caregivers who were not vulnerable.
The research was supported by grants from the National Institutes of Health.
Psychosomatic Medicine is the official peer-reviewed journal of the American Psychosomatic Society, published bimonthly. For information about the journal, contact Joel E. Dimsdale, M.D., editor-in-chief, at 619-543-5468.
Posted by the Center for the Advancement of Health http://www.cfah.org. For information about the Center, contact Petrina Chong pchong@cfah.org, 202-387-2829.
Journal
Psychosomatic Medicine