Tuesday, 17 December 2019

Does vaping cause respiratory disease?

Junk science supremo Stanton Glantz returned this week, with his colleague Dharma Bhatta, to claim that vaping causes chronic obstructive pulmonary disease (COPD), chronic bronchitis and asthma. In a study published in the American Journal of Preventive Medicine and widely reported in the media, the duo use the publicly accessible PATH survey to look at rates of disease in a large American sample between 2013 and 2016.

All told, they reckon that vaping increases the risk of respiratory disease by around 30 per cent. In comments to the press, Glantz said:

“Based on what we know about the biological effects of e-cigarettes, my guess is that if we followed these people for 20 years, the e-cigarette effect would be similar [to the risks associated with smoking,]”

The study has two sets of results. Firstly, it looks at the prevalence of disease among vapers, former vapers and smokers in the first wave of 2013/14.

Secondly, it looks at the prevalence of new cases of disease between the first wave of 2013/14 and the second and third waves of 2014-16.

In each case, they find that the risk of respiratory disease is around 30 per cent higher for both vapers and ex-vapers (the risks are higher for smokers).

There are a number of problems with this. First and foremost, COPD and chronic bronchitis only develop in smokers after decades of daily cigarette use. Given that e-cigarettes had only been on the market for a few years in 2013, it is biologically implausible that vaping could cause the same effects.

The mechanism by which vaping could cause new cases of asthma is even more mysterious. Although asthma can be exacerbated by smoking, it isn't caused by smoking.

Glantz and Bhatta don't manage to find a statistically significant association between vaping and COPD but they do find an 82% increased risk of COPD among former vapers (1.82 (1.23, 2.69)). This is even more extraordinary. Since almost nobody was vaping before 2010, we are being asked to believe that there are people out there who vaped for a year or two, quit and then developed COPD as a result.

'As a result' is the key phrase. Glantz and Bhatta insist that there is direct causality at play; that their findings are independent of all other factors except e-cigarette use. They reject the obvious explanation - that vapers are nearly all smokers and ex-smokers and are therefore bound to be at greater risk of respiratory disease than the never-smokers/vapers to whom they are being compared.

Of the e-cigarette users in the first wave of 2013/14, 85.5% were also smokers and 13.9% were former smokers. Only 0.6% said that they had never smoked. The claim that vaping causes COPD and chronic bronchitis is therefore based on a group of vapers of whom 99.4% are current or former smokers!

If you wanted to study the effects of vaping independently of smoking, you would compare people who have vaped but never smoked with people who never vaped or smoked. Glantz and Bhatta have the data with which to do this, but they choose not to. Instead, they lump never-smokers, ex-smokers and current smokers together in a group called 'vapers' and then claim to have controlled for smoking.

It is debatable whether the dataset they use allows such adjustments to be made. It is not even clear whether 'controlling for combustible tobacco use' is realistically possible. Glantz and Bhatta do not explain how they went about doing it, so we are left in the position of having to trust them.

They have done nothing to deserve such blind faith. Last year, they produced a study based on the same dataset and claimed that vaping doubles the risk of having a heart attack. Thanks to Brad Rodu, we later discovered that a large number of the heart attacks took place before the individuals had ever used an e-cigarette. The study was such a shoddy piece of work that it gained some media attention and several academics have been trying to get it retracted.

And that's before we get onto Glantz's long career driving the tobacco control clown car and his fanatical opposition to e-cigarettes.

So no, I don't trust these two to control for a variable that runs through the dataset like a stick of rock and which is almost certainly the true cause of the statistical associations reported. It is extraordinarily unlikely that vaping for a few years could cause any of the diseases studied (if it did, their rates would have skyrocketed in recent years - they haven't).

I hate to quote John Britton, but he is on the money in his letter to the Times today...

He's right. It's trash. Ignore it.

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