People exposed to higher levels of Bisphenol A (BPA), a chemical widely used in food packaging, may have a slightly higher risk of heart disease, according to UK researchers.
They can't say for sure if some factor other than BPA, like weight or blood pressure, might be the underlying reason for the heart problems. Still, this is the third study from the team to find such a link.
"We've now shown this association in two quite separate ways, in completely different people... and at very different exposure levels," said lead researcher Dr. David Melzer of Peninsula Medical College in Exeter, UK. "It's getting a bit intriguing, really."
BPA's potential health effects are controversial. The chemical is used in countless consumer products, including drinking bottles and the lining of tin cans.
The U.S. Food and Drug Administration, which originally stated that the chemical was safe, is now rethinking that position. According to the agency's website, "recent studies provide reason for some concern about the potential effects of BPA on the brain, behavior, and prostate gland of fetuses, infants and children."
The FDA has reportedly said it will decide at the end of this month if BPA should be banned from food and beverage packaging.
Exposure to BPA has been tied to behavioral problems in girls, a hormonal syndrome in women, and a variety of physiological effects in animals (see Reuters Health stories of October 24, 2011 and January 11, 2011).
But whether BPA is actually to blame for these health problems is still a matter of debate.
In 2008 and again in 2010, Melzer and his colleagues reported that people with heart disease were more likely to also have higher levels of BPA in their urine than people without heart disease.
Those studies only took a snap shot in time of people's BPA levels and whether or not they had heart disease. That makes it hard to tell which came first -- the elevated chemical levels or the clogged arteries, also called coronary artery disease.
To find out, the team started its latest study with a large group of Britons who didn't have heart disease.
Each of the participants provided a urine sample. On average, people had a BPA concentration of 1.3 nanogram per milliliter (ng/mL) urine, which Melzer said was lower than the concentrations found in his earlier studies on US residents.
The researchers then tracked over a decade who developed coronary artery disease and who didn't. They compared the BPA levels of 758 people who ended up with heart disease with those of 861 people who remained free of heart issues.
For each increase in BPA concentration of 4.56 ng/mL, there was a 13 percent greater risk of heart disease across the participants in the study.
However, after accounting for factors like blood pressure, weight, exercise and social class, the link between BPA and heart disease was no longer statistically reliable, the researchers found.
Coronary artery disease is the leading cause of death of Americans, and it affects about one in five people over age 65.
Even if BPA is actually involved in heart problems, it would still be a minor risk factor compared with things like smoking and obesity.
"There's no suggestion that BPA is more important than traditional risk factors," said Melzer.
He also cautioned against putting too much stock in the accuracy of the risk estimate, because his study used only one urine sample for a decade-long follow up.
More importantly, he said, is that the research agrees that there is some relationship between BPA and heart disease.
"There's always the possibility it's not BPA that explains these findings, but now that we've found it three times, we need to get more data from humans," he told Reuters Health.
There is still no clarity about how BPA would take a toll on the heart, should that turn out to be the case. Melzer suggested it would be valuable for future studies to either add or subtract the chemical from people's diets to see how it affects their health.