Don’t throw out your frypans: CVD-Teflon link not necessarily strong

The past week has seen a slew of sensationalist headlines claiming that using non-stick frypans can give you heart disease. Before you rush home to cleanse your kitchen of Teflon pans, read on. It seems there’s more to this story than meets the eye.

While a number of media groups have seized on the idea that cardiovascular disease is linked to a chemical used in non-stick cookware, a closer inspection of the report reveals that this is not necessarily the case. But then “Non-stick cookware might give you heart disease; then again, maybe it won’t” isn’t exactly an attention-grabbing headline, is it?

The study

Researchers from the West Virginia University (WVU) School of Public Health published a study, Perfluorooctanoic Acid and Cardiovascular Disease in US Adults, online in the Archives of Internal Medicine. The study claimed to find an association between high levels of PFOA - also known as C8 - and cardiovascular disease. The chemical is used in the manufacture of household products like water bottles, clothing, paints, cosmetics and non-stick cookware. An estimated 98% of the US population have PFOA at detectable levels in their blood.

The research team, led by Dr Anoop Shankar, reported that they examined 1216 subjects from the 1999-2003 National Health and Nutritional Examination Survey (NHANES) and found that increased PFOA levels were positively associated with cardiovascular disease (CVD) and peripheral artery disease (PAD).

But the study’s findings are by no means a foregone conclusion. A statement published on the university’s own website cautions that, although an association was found, “this is a very preliminary study and [the research team] has only discovered an association between the two, not causality”.

The lead researcher even admits to the limitations of the findings. “These two factors - increased PFOA levels and cardiovascular disease - are co-existing together for some reason,” Shankar said. “To determine the cause and effect, we would have to do follow-up studies over time, which we are, in fact, doing. At this point, we cannot say that one caused the other.”

So the researchers have found a tenuous link between a chemical that’s found in a number of items people encounter on a regular basis and CVD in a small sample from over a decade ago. Hardly groundbreaking stuff. And hardly a conclusive link between non-stick cookware and heart disease, as the sensational headlines would have us believe.

Kiwis on the case

An academic from the University of Auckland has raised serious doubts about the importance of the WVU study in an online article entitled ‘Attack of the killer frying pans’. Author Thomas Lumley, a Professor of Biostatistics, says the newspapers claiming non-stick cookware is linked to heart disease have the wrong end of the stick (or wok, as the case may be).

“PFOA is used to make non-stick cookware, but cooking with non-stick cookware isn’t an especially important source of it, and the article doesn’t say it is,” Lumley wrote.

Lumley also takes aim at the researchers’ methods, querying their use of data from two non-adjacent two-year periods - a method that even the least mathematically minded among us might consider odd. Lumley looked at more recent data drawn from the same source and found that “there is absolutely no sign of an association between coronary heart disease and PFOA levels in the 2007-2008 data”.

The researchers’ classification of subjects was also questionable, Lumley found. Subjects were defined as having heart disease based not only on a doctor’s analysis but by response to the question, “Has a doctor ever told you that you had coronary heart disease?” Hardly an objective method of establishing cardiovascular health.

The voice of reason

Dr Ian Musgrave similarly questions the link between PFOA and cardiovascular disease. Writing for The Conversation, Musgrave - a senior lecturer in Pharmacology at the University of Adelaide - argues that “actual long-term exposure to PFOA may be very different from that suggested by a single measurement”. In fact, Musgrave writes, at the time of the WVU study, PFOA levels in blood were falling as a result of PFOA regulation.

Additionally, those with high PFOA blood levels had significant differences in lifestyle, education and background from those with low PFOA levels. “PFOA may simply be a marker for low socioeconomic status, which itself is known to be correlated with risk of cardiovascular disease,” Musgrave argues.

Just when you thought there couldn’t possibly be another hole in the WVU study, Musgrave finds another. “Unusually,” he writes, “the association [between PFOA and CVD] disappeared in smokers and people with body mass indexes less than 30.”

Musgrave echoes Shankar’s comment on the need for follow-up studies. “The current study is suggestive, but is a long way from showing that exposure to the background levels of PFOA in our environment harms our heart and blood vessels.

“It requires follow-up with studies that track exposure to PFOA to better understand the possible role of PFOA in cardiovascular disease,” Musgrave wrote.

Having considered the study, Musgrave issues some sage advice to the public: “We should keep an eye on levels of perfluorinated compounds and try to minimise our exposure to them as a matter of course, but there is currently no good evidence that the levels most of us are exposed to are harmful.”

Let’s hope the one quiet voice of reason is heard amongst the screaming of the multitudinous sensationalist headlines.