Stress has long been linked to an increased risk of heart attack. But now researchers say there's a way to measure chronic stress by analyzing a strand of hair.
The hormone cortisol is made and released into the blood by the adrenal glands during moments of high stress. Hair follicles are exposed to whatever circulates in the bloodstream, so more cortisol circulating in the blood means more cortisol ends up in a strand of hair, said study researcher Dr. Stan van Uum of the University of Western Ontario in Canada.
"So by using this hair, now we can look back in time before the heart attack occurs," van Uum told MyHealthNewsDaily.
On average, hair grows a little less than half an inch (one centimeter) each month, so a strand of hair five inches (12 centimeters) long, would provide a year's worth of information on cortisol levels, he said.
That time frame is different from what can be measured by other methods of determining cortisol levels, which include testing urine, blood and saliva, according to the researchers. These methods don't test ongoing stress hormone levels, they only provide a "snapshot" of the levels at the time of the collection of the bodily fluid.
Testing hair is "like a retrospective calendar for exposures that the body undergoes," he said. "Hair grows day and night, so it's a reflection of 24-hour periods."
Although stress has been linked to heart attacks, it has not been shown to directly cause them, or to cause high blood pressure. However, it affects overeating, drinking and smoking, and therefore raises risks for heart attack and stroke, according to the American Heart Association.
Van Uum and fellow researcher Dr. Gideon Koren studied 1.5-inch (3-centimeter) long hair samples from 56 male adults admitted to the Meir Medical Centre in Israel for heart attacks, in addition to 56 males admitted for non-heart-attack related reasons. The researchers found higher cortisol levels for all the men who had come in for heart attacks, even after outside risk factors like diabetes and hypertension were accounted for.
The findings of the study are important in seeing how preventive programs for stress can help decrease the risk for heart attack, van Uum said, and in showing how future research on cortisol levels can be done.
"There are things you can change and things you can't [about heart attack risks], like men have a higher risk than women," he said. But "it gives a sense for how aggressive you need to be with other factors. What we'd like to study next is can we, in some way, bring down stress?"
The study was published Sept. 3 online in the journal Stress.