Doctors have long cautioned that there is a correlation between chronic stress and heart disease, but until now, it wasn’t known exactly how the two were connected. Now, researchers from Harvard Medical School and Massachusetts General Hospital have found what they believe is the missing link: overproduction of white blood cells, or leukocytes. Excess white blood cells contribute to blood vessel inflammation and plaque accumulation in the arteries, upping the risk for blood pressure problems, stroke, and heart attack.
Normally, white blood cells are beneficial – they help your body fight infection and aid healing. “But if you have too many of them, or they are in the wrong place, they can be harmful,” said study co-author Matthias Nahrendorf of Harvard Medical School.
When a person is stressed, the body goes into overdrive producing the white blood cells, which Nahrendorf said makes sense. “An enlarged production of leukocytes prepares you for danger, such as in a fight, where you might be injured. But chronic stress is a different story — there’s no wound to heal and no infection.”
For the study, researchers examined medical residents working in the Intensive Care Unit, a job that sees all manner of trauma and requires life-or-death decisions to be made every day. They found that the residents had extremely high levels of white blood cells. Next, the researchers studied stressed-out mice and found that they, too, seemed to be over-producing white blood cells.
The problem of stress leading to excess white blood cells, plaque buildup, and blood flow problems is only compounded when you consider that heart disease is the leading cause of death in the United States. Heart disease kills more people in this country than AIDS and all cancers combined — close to one million per year.
Previously, it was thought that a high white blood cell count was a sign of inflammation in the body – now, Nahrendorf and his team believe that too many white blood cells may actually be triggering the inflammation.
These findings raise the possibility of monitoring white blood cell count to help measure how much stress that patients are under and to flag individuals who may be at risk for heart disease.