Sept. 9, 2010 -- Doctors have long warned patients that stress is bad for the heart. Now new research provides direct evidence to back up the warning.
In the newly published study, high levels of the stress hormone cortisol in the urine were associated with a dramatic increase in death from cardiovascular disease years later.
Compared to study participants with the lowest cortisol levels, those with the highest levels were five times as likely to die of heart attack, stroke or other cardiovascular causes over six years of follow up.
The association was seen both in people with and without heart disease when they entered the study.
While earlier research suggested a link between high cortisol levels and cardiovascular risk, the study is the first to directly test the hypothesis that elevated stress hormones predict heart disease death, says lead researcher Nicole Vogelzangs, PhD, of VU University Medical Center in the Netherlands.
“We were actually surprised to find that the association was so strong,” Vogelzangs tells WebMD. “Cortisol levels in older adults were clearly predictive of death from cardiovascular causes, but were not predictive of other causes of death.”
The study was published less than a week after a separate team of researchers reported that high levels of the hormone in hair samples predict heart attack risk.
Cortisol Predicts Heart Health
Secreted by the adrenal glands, cortisol is known as the "stress hormone" because it is produced in high levels as the body’s "fight or flight" response to stressful events.
Prolonged cortisol production resulting from chronic stress is thought to play a role in a wide range of diseases, including diabetes, osteoporosis, and heart disease.
Cortisol can be measured in the blood, but blood measurements show only a snapshot of stress at the moment, which may be elevated in response to having blood drawn, Vogelzangs says.
In the new study, published in the Journal of Clinical Endocrinology & Metabolism, researchers measured cortisol levels over a 24-hour period in urine samples.
The study included 861 people aged 65 and older followed for an average of about six years after 24-hour cortisol levels were measured.
During this time, 183 study participants died. Death certificates were examined to determine the cause of death.
While urinary cortisol did not predict death from non-cardiovascular causes, it strongly predicted death from heart attack and stroke.
When divided into three groups based on levels of the stress hormone, the third of study participants with the highest cortisol levels had a fivefold increased risk of dying from cardiovascular causes as the third with the lowest levels.
Clinical Value of Stress Hormone Test Not Clear
In the study reported earlier this month, researchers from the University of Western Ontario measured cortisol levels in hair samples as a marker of chronic stress.
Study co-researcher Stan VanUum, MD, PhD, explains that hair grows at a rate of about 1 centimeter a month. So a 3 centimeter hair sample would measure stress levels over 3 months.
The researchers found that hair cortisol levels were a more important predictor of heart attack risk than established risk factors like high blood pressure and cholesterol.
VanUum and Vogelzangs agree that more research is needed to determine if stress hormone measurement can provide meaningful information about heart risk in clinical practice.
There is no consensus about what "high" and "normal" cortisol levels should be in terms of cardiovascular risk. And measuring levels of the hormone in hair remains expensive and labor intensive.
While there is some suggestion that cortisol levels might be reduced with exercise, weight loss or even the use of antidepressants, it is far from clear if directly targeting cortisol lowers cardiovascular risk.
“These studies reinforce the message that stress is bad for the heart, but we don’t really know if we can reduce stress hormone levels or what impact this would have,” VanUum tells WebMD.