If our eyes are the window to our soul, might our hair be a window into our heart attack risk?

Canadian researchers think it might be, suggesting that clues found in our hair could signal if we could be headed to the cardiologist.

According to a new study, measuring levels of the stress hormone cortisol in our hair may be a good way to screen for chronic stress and our risk for a heart attack.

While it's long been theorized that chronic stress can put one at risk of heart disease and heart attacks, there's never been a good way to objectively measure chronic stress. Instead, most studies on chronic stress and heart attacks have used questionnaires to ask patients about their stress levels.

So Drs. Gideon Koren and Stan Van Uum from the University of Western Ontario developed a method to measure cortisol levels in hair, which they say provides an accurate assessment of stress levels in the months prior to a heart attack.

"Intuitively we know stress is not good for you, but it's not easy to measure," Koren, who holds the Ivey Chair in Molecular Toxicology at Western's Schulich School of Medicine & Dentistry said in a news release.

His team notes that while blood, urine and saliva can also contain indicators of stress, cortisol captured in the hair shaft remains stable for months -- even years. In fact, researchers have been able to detect cortisol in the hair of ancient Peruvian mummies dating back to AD 550-1000.

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

In the study, hair samples three centimetres long were collected from 56 men who were admitted to the Meir Medical Centre in Kfar-Saba, Israel, suffering heart attacks. A control group of 56 men, who were hospitalized for reasons other than a heart attack, was also asked for hair samples.

When the researchers measured the cortisol levels in the hair of the two groups, they found higher cortisol levels corresponding to the previous three months in the heart attack patients, compared to the control group.

The researchers did note that the patients who'd had heart attacks also had more cholesterol problems. But their blood pressure problems were about the same, as was their family history of coronary artery disease.

After accounting for the known risk factors, hair cortisol content emerged as the strongest predictor of heart attack, the researchers said.

The study, published in the journal Stress, was funded by Physician Services Inc. and CIHR, the Canadian Institutes of Health Research.