Researchers at the University of Western Ontario are the first to use a biological marker in human hair to provide direct evidence that chronic stress plays an important role in causing heart attacks. In the past, chronic stressors such as job, marital and financial problems, have all been linked to an increased risk for developing cardiovascular disease and heart attack, but until now there hasn’t been a biological marker to measure the major risk factors.

“Intuitively, we know stress is not good for you, but it’s not easy to measure,” explains Dr. Gideon Koren, who holds the Ivey Chair in Molecular Toxicology at Western’s Schulich School of Medicine and Dentistry. “We know that on average, hair grows one centimeter a month, so if we take a hair sample six centimeters long, we can determine stress levels for six months by measuring the cortisol level in the hair.”

Cortisol is widely considered to be the main stress hormone, because stress activates its secretion. Traditionally, it’s been measured in blood serum, urine and saliva, but that only monitors stress at the time of measurement, not over longer periods of time.

In the study, hair samples three centimeters long, corresponding to about three months of hair growth, were collected from hospitalized patients who had suffered a heart attack, and then compared with hair samples from other patients. The heart attack patients were found to have significantly higher levels of cortisol in their hair, compared to the control group. This finding provides a new, non-invasive way of testing a patient’s risk.