Studies: BPA may cause heart problems in women
Saturday June 13, 2009 (foodconsumer.org) -- Bisphenol A (BPA) may be harmful for the heart, particularly in women, according to several studies presented in Washington, D.C. at ENDO 09, the Endocrine Society's annual meeting.
Studies suggest that people with cardiovascular disease have higher levels of BPA in their urine.
One study led by Dr. Scott Belcher, of the department of pharmacology and cell biophysics at the University of Cincinnati, found exposure to BPA and or estrogen causes abnormal cardiac activity in female rats and mice.
Researchers also found that estrogen receptors in heart muscle cells are responsible for the effect. BPA, officially recognized as an environmental pollutant, is estrogenic and can interact with the receptors.
Previous studies suggest exposure to BPA may cause problems with development of the reproductive system and the brain among other things.
"We had reason to believe that harmful cardiovascular affects can be added to the list," said Belcher, according to a UC press release.
BPA is used to make hard polycarbonate plastic, such as for baby bottles, refillable water bottles and food containers, as well as to make the linings of metal food cans. It has been linked to an increased risk of neurological defects, diabetes and breast and prostate cancers.
For the current study, Belcher and his team exposed cardiac cells isolated from rat or mouse hearts to BPA, and or estrogen, and found both caused abnormal activity of cardiac muscle cells in women, but not men.
Additional studies revealed that the change caused improper beating or an increased frequency of arrhythmias, or heartbeat irregularities in the female heart.
"Low doses of BPA markedly increased the frequency of arrhythmic events," Belcher said. "The effect of BPA on these cardiac arrhythmias was amplified when exposed to estradiol, the major estrogen hormone in humans."
The researchers used cellular imaging techniques to investigate the mechanism underlying this harmful effects and found that BPA, and or estrogen, rapidly stimulated contraction by altering control of the concentrations of free intracellular calcium in female heart muscle cells.
"BPA's presence increased the frequency of calcium 'sparks' from the sarcoplasmic reticulum—the part of the cardiac muscle that stores and releases calcium ions—indicating spontaneous release or 'leak' that's likely causing the heart arrhythmias and may have other harmful actions, especially following heart attack," stated Belcher.
"These studies have identified new and important potential cardiac risks associated with BPA exposure that may be especially important for women's heart health," he said.
Another study led by Dr. Hugh Taylor, professor and chief of the reproductive endocrinology section at Yale University School of Medicine, explained that exposure to BPA early in pregnancy may cause a fertility defect in the offspring.
Specifically, Taylor and colleagues found mice born to mothers that were exposed to a low dose of BPA in early stages of pregnancy (9 to 16 days) had their uterine function changed.
They found that BPA exposure during pregnancy affected a gene known as HOXA10 that is responsible for uterine development and fertility in both mice and humans. The exposure resulted in a permanent increase in estrogen sensitivity.
"We don't know what a safe level of BPA is, so pregnant women should avoid BPA exposure," Taylor said. "There is nothing to lose by avoiding items made with BPA -- and maybe a lot to gain."
(David Liu and edited by Sheilah Downey)
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The study, published in the March 3 issue of the Journal of the American College of Cardiology, may demonstrate a link between mental stress and sudden cardiac arrest, which causes more than 400,000 deaths every year.
Arrhythmias, which are heart rhythm problems, happen because of a malfunction in the electrical impulses in your heart that coordinate heart beats, according to the Mayo Clinic. The result is that your heart beats too fast, too slow or irregularly.<BR>
Some arrhythmias may increase a person's risk of stroke or congestive heart problems.<BR>
This study is relevant to people who have heart disease already, said study author Dr. Rachel Lampert, associate professor at Yale University School of Medicine.t<BR>
"Perhaps if we treat them with something like stress management or anger management, we may decrease the likelihood of arrhythmias," she said.
Previous research has shown that the rate of sudden cardiac death increases when the population is collectively stressed, such as during an earthquake or war, Lampert said.<BR>
Other studies have also shown that if you ask patients about what happened before a heart attack, they'll most frequently say they were angry, said Dr. Charles Raison, psychiatrist and director of the Mind/Body Institute at Emory University in Atlanta, Georgia.
"It is just indisputable that negative emotionality -- especially anger and misery, depression -- are terrible for your heart,"<BR>
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Researchers looked at 62 patients with implantable cardioverter-defibrillators, devices that monitor heart rhythms and emit painful shocks in response to dangerous rhythms.
The patients were asked to describe a time in the previous couple weeks when they felt angry or aggravated, and were prompted with questions to describe the moment vividly. Researchers looked at the heart's electrical stability through a measure called T-wave alternans.
"Overall in the group, when we did the anger recall protocol, the group as a whole showed an increase in electrical instability," Lampert said.
Researchers then compared the top 25 percent of people -- those who showed the most instability -- with the others in the group and found that the the ones with the highest instability in the lab were 10 times more likely to experience an arrhythmia sometime in the next three years.
The idea could be used as a predictive test for people who are unable to take an exercise-induced electrical stability test, Lampert said.
More study is needed to see how the mental stress test relates to traditional exercise testing, said Dr. Eric Rashba, professor of medicine at Stony Brook University Medical Center in Stony Brook, New York. Rashba was not involved in the study. The new test may be useful in combination with the exercise test, he said.
While this is an early study with a small sample size, it is the first time this type of anger or emotional stress testing has been shown to correlate with future arrhythmias, he said.
Exercise elevates heart rate much more than mental stress does, meaning the effects of mental stress on the heart may be caused by adrenaline impacting the heart cells, the study authors said.
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