Chronic stress plays an important role in heart attacks, according to an Israeli-Canadian study of stress hormone levels in hair.
Ongoing psychological stressors such as job strain, marital problems and financial stress have been linked to a higher risk of developing cardiovascular disease, including heart attacks, but not all studies have found such links.
Some studies used questionnaires that asked people to recall stress levels, which might be difficult to remember accurately. Scientists have been looking for a biological marker to test the role of chronic stress in heart attacks.
Cortisol, a hormone secreted in higher levels during times of stress, is traditionally measured in blood, urine or saliva. But those measurements reflect stress only at a certain period of time, not over long stretches.
Hair, however, captures cortisol levels over a longer period, said study author Dr. Gideon Koren, who holds the Ivey chair in molecular toxicology at the University of Western Ontario in London.
Since hair grows one centimetre per month on average, a six-centimetre-long hair sample can show cortisol levels over six months, he said.
"It gives us, for the first time, a biological marker for chronic stress," Koren said.
The hair shaft records cortisol levels through time, similar to the way tree rings reflect age.
In the study, published in Friday's online issue of the journal Stress, researchers collected three-centimetre-long hair samples from 56 men admitted to the Meir Medical Centre in Kfar-Saba, Israel, suffering heart attacks or acute myocardial infarction (AMI).
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A control group of 56 who were treated in hospital for reasons other than a heart attack also provided hair samples.
"In conclusion, hair cortisol concentrations were found to be elevated in the three months prior to the event in patients admitted with AMI, than in controls," the study's authors wrote.
"Hair cortisol measurements can be used to identify patients at high risk for AMI who may benefit from strategies targeted to manage chronic stress, and as an impetus for more aggressive treatment of other modifiable risk factors."
Risk factors like hypertension, smoking and family history were similar in both groups, but the heart attack patients had more cholesterol problems.
After taking known risk factors into account, hair cortisol levels was the strongest predicator of heart attack, the researchers said.
But the study's authors noted the hair sample needs to be long enough and the findings could be subject to contamination by creams containing cortisol.
The study has implications for doctors, since stress can be managed with lifestyle changes and psychotherapy, Koren said.
Dr. Chris Glover, a cardiologist at the University of Ottawa Heart Institute and an assistant professor of medicine at the University of Ottawa, said he's unsure how the findings could help in identifying or treating stressed patients.
"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," Glover said.
"I think you have to do a lot more work to show that."
Lou Eisen, a Toronto man who had a heart attack five years ago, said he felt under so much stress at the time that his hair "may have exploded."
Eisen said the test sounds simple to do and likely well worth it.
The researchers also plan to test cortisol levels in the hair of women.
The study was funded by Physician Services Inc. and the Canadian Institutes of Health Research.
The test is not patented.