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In the not too distant future, your family doctor may pluck a hair from your head to see if you're in imminent danger of a heart attack.

That's because your hair contains an accurate record of your body's production of cortisol - a hormone that surges through your body when you're under stress. And stress can be the trigger for a potentially deadly cardiac event.

Researchers at the University of Western Ontario say they have developed a test to measure cortisol levels in hair. What's more, they have used the test to show that the stress hormone can be exceedingly high in the months preceding a heart attack.

"Intuitively, we know that stress is not good for you, but it's not easy to measure," said Gideon Koren, who holds a research chair at Western's Schulich School of Medicine & Dentistry.

Traditionally, cortisol has been measured from blood, urine or saliva samples, but these tests provide a limited picture of stress levels for only a few days. And psychological questionnaires aren't much better at reliably gauging an individual's stress levels over a long period of time.

So Dr. Koren and his research colleagues latched on to the idea of testing a shaft of hair, which incorporates a wide range of bodily substances - including cortisol - into its structure as it grows.

"We know that on average hair grows one centimetre a month, and so if we take a hair sample six centimetres long, we can determine stress levels for six months by measuring the cortisol level in the hair," he said.

With their newly developed test in hand, the researchers recruited 56 men who had been admitted to hospital after suffering a heart attack. Shafts of hair were taken from each volunteer and compared with samples collected from 56 male patients who didn't have heart attacks.

The study revealed "significantly higher" cortisol levels in the heart attack patients compared with the control group, according the results published Friday in the journal Stress.

Dr. Koren noted that many factors can contribute to the emergence of heart disease, including high blood pressure, diabetes, smoking, cholesterol levels and genetic predisposition - traits shared by a lot of the men in the two groups of the study.

When these various risk factors were taken into account, hair cortisol content emerged as the strongest predictor of a heart attack, the researchers report.

Of course, studies involving a broader range of patients, including women, will be needed to establish the test's true worth. But it holds out the promise that doctors will be able to pinpoint those patients who need prompt stress management - and possibly help them prevent a heart attack.