TORONTO (Canadian Press) -- Whether you're sporting a cropped cut or long curls, your hair may do more than reflect your personal style - researchers say it may serve as a means to measure stress.

According to a new study, a stress hormone that's captured in the hair may act as a biological marker for chronic stress, which researchers suggest may serve as a predictor of heart attacks.

"Acute stress is relatively simple," said Dr. Gideon Koren, who holds the Richard Ivey Chair in Molecular Toxicology at Schulich School of Medicine & Dentistry at the University of Western Ontario.

"You can talk to people, there are psychological ways to ask them (about) their stress ... and you can measure blood, urine to look at how much cortisol they secrete - cortisol, of course, being the stress hormone."

"Much less is known about chronic events."

Unlike blood, urine and saliva, which are indicators of stress at the time when measured, researchers say cortisol captured in the hair shaft remains stable within locks for months, even years. In fact, they point to a recent study that revealed the presence of cortisol in the hair of ancient Peruvian mummies dating back to AD 550-1000.

So Koren, along with researchers from Western and Meir Medical Center in Kfar-Saba, Israel, decided to explore a possible link between chronic stress and heart attacks by developing a method to measure cortisol in hair.For the small study, published online in the journal Stress, hair samples at least three centimetres in length were analyzed from two groups, each with 56 male patients: those who had had heart attacks and those who hadn't.Koren said men who had heart attacks had "significantly higher levels of cortisol" compared to those male patients who didn't, even after correcting for other risk factors.

While the prevalence of diabetes, hypertension, smoking and family history of cardiovascular diseases didn't differ much between the two groups, low-density lipoprotein (LDL) or so-called "bad" cholesterol levels and body-mass index were significantly higher among the heart attack patients.

Heart attack patients as a group had higher hair cortisol measurements, but a patient who didn't suffer a heart attack had the highest individual recorded number.

Researchers also point to limitations in using hair cortisol measurements. There has to be a sufficient length of hair, and it could potentially be "subject to contamination by cortisol-containing creams."

Also, since the hair follicle lies about three millimetres beneath the scalp, cortisol measured in hair doesn't reflect immediate or recent exposure.

Koren said this was a "conceptual paper" and they plan to do more work in the area, including testing that includes women. Still, he said he has no doubt that this is an "avid marker."

"Indeed, we do not think this will solve the whole issue of heart attacks - clearly not," Koren said. "But if somebody has for example, other risk factors, like hypertension and diabetes, a certain amount of stress can be very detrimental for them."

"Hopefully with more studies, we can come up with numbers that can be used to warn people, because you can modify stress levels, people can do different things."

As for bald individuals, could the test be conducted using hair found elsewhere on the body? Koren said there's uncertainty about whether the rate of growth will be good.

"To use those areas, much more work will have to be done and we intend to do it, of course."

Dr. Chris Glover, a cardiologist at the University of Ottawa Heart Institute and an assistant professor of medicine at the University of Ottawa, said while the study is interesting, it doesn't add any more than what is already known.

Glover said in big studies, chronic stress, specifically seen in people with depression and anxiety disorders, as well as acute lifestyle stresses - like the death of a spouse or child, or divorce - are also associated with higher risk of having a heart attack.

While researchers say that hair grows on average by around one centimetre each month, Glover said there's variability in terms of hair growth, and the process actually slows as you age. Other hormonal effects can also have an impact.

Since the researchers didn't include a behavioural stress scale questionnaire, there could be other reasons people recorded higher cortisol levels aside from chronic stress, Glover noted.

He also said cortisol is something that is variable throughout the day, and individuals may get a surge if they're stressed.

"If you're chronically stressed, it's hard to know if your cortisol levels will be up more than it would be if you just had one, big acute stress or vice versa," he said.

Glover said he's unsure of where the findings fit in with either identifying or treating patients with stress.

"I'm not really sure that taking someone that comes in and says, `I don't have any stress,' and then taking a hair sample that says, `Your cortisol's up, we've got to do something about your stress' - I don't think this shows that would be valid," he said.

"I think you have to do a lot more work to show that."

The Canadian Press, 2010