New research finds that those carrying the highest levels of bisphenol A may have a higher risk of heart disease.
Bisphenol A, or BPA, is a chemical used to soften plastics. It's been removed from baby bottles sold in Canada over worries about its safety, because it mimics the hormone estrogen. But it is still used in many plastic products and in the coating of food and beverage cans.
It's such a prevalent chemical that it's been estimated it can be detected in the bodies of more than 90 per cent of Americans, and likely Canadians too.
Years ago, the U.S. Centers for Disease Control undertook to investigate the prevalence and safety of BPA in humans. It began testing for the chemical in a representative sample of Americans, as part of the 2003-2004 arm of the huge NHANES data-collection study.
In 2008, University of Exeter researcher David Melzer led a U.K. research team that analyzed the data and found that high BPA levels were linked to a higher risk of heart disease, diabetes, and elevated liver enzymes.
Now Melzer's team has released the results of their analysis of a new set of NHANES data, collected in 2005-2006. They found, surprisingly, that average BPA levels were 30 per cent lower in the more recent study, though no one's sure why.
But they also found that the BPA-heart disease link held, despite the drop in average levels. Those with the highest BPA levels still had a significantly higher risk of heart disease, confirming to Melzer that the link is real.
Melzer calculates that a 60-year-old man in the top third of BPA levels (who would have over 3.5 nanograms/milliliter urinary concentration) has a 10.2 per cent chance of having heart disease. A 60-year-old man in the lowest third of BPA levels (under 1.4 ng/mL urinary concentration) has a 7 per cent chance of having heart disease.
That works out to about a 45 per cent greater risk of heart disease in the higher BPA level group.
The study also found that while data from the earlier survey suggested a link between BPA and adult-onset diabetes, that link was weaker in the second survey.
Melzer says the figures, published in the open-access journal PLoS One, may be an underestimation of the true heart disease risk. That's because urinary concentrations of BPA are only an approximate marker of longer-term BPA exposure.
While the study shows a link between BPA and heart disease, it doesn't proves that BPA causes heart disease. Longitudinal studies that track people with high BPA levels over time might provide clearer answers.
Statistics Canada has taken BPA samples in about 5,000 people, the largest such bio-monitoring effort in the world, and expects to report results this summer.
