In pursuit of a nebulous metaphor…

I don’t believe in god, but if he/it/she/they existed, then his/its/her/their gift to science communication would’ve been the metaphor. Metaphors help make sense of truly unknowable things, get a grip on things so large that our minds boggle trying to comprehend them, and help writers express book-length concepts in a dozen words. Even if there is something lost in translation, as it were, metaphors help both writers and readers get a handle on something they would otherwise have struggled to.

One of my favourite expositions on the power of metaphors appeared in an article by Daniel Sarewitz, writing in Nature (readers of this blog will be familiar with the text I’m referring to). Sarewitz was writing about how nobody but trained physicists understands what the Higgs boson really is because those of us who do think we get it are only getting metaphors. The Higgs boson exists in a realm that humans cannot ever access (even Ant-Man almost died getting there), and physicists make sense of them through complicated mathematical abstractions.

Mr Wednesday makes just this point in American Gods (the TV show), when he asks his co-passenger in a flight what it is that makes them trust that the plane will fly. (Relatively) Few of us know the physics behind Newton’s laws of motion and Bernoulli’s work in fluid dynamics – but many of us believe in their robustness. In a sense, faith and metaphors keep us going and not knowledge itself because we truly know only little.

However, the ease that metaphors offer writers at such a small cost (minimised further for those writers who know how to deal with that cost) sometimes means that they’re misused or overused. Sometimes, some writers will abdicate their responsibility to stay as close to the science – and the objective truth, such as it is – as possible by employing metaphors where one could easily be avoided. My grouse of choice at the moment is this tweet by New Scientist:

The writer has had the courtesy to use the word ‘equivalent’ but it can’t do much to salvage the sentence’s implications from the dumpster. Different people have different takeaways from the act of smoking. I think of lung and throat cancer; someone else will think of reduced lifespan; yet another person will think it’s not so bad because she’s a chain-smoker; someone will think it gives them GERD. It’s also a bad metaphor to use because the effects of smoking vary from person to person based on various factors (including how long they’ve been smoking 15 cigarettes a day for). This is why researchers studying the effects of smoking quantify not the risk but the relative risk (RR): the risk of some ailment (including reduced lifespan) relative to non-smokers in the same population.

There are additional concerns that don’t allow the smoking-loneliness congruence to be generally applicable. For example, according to a paper published in the Journal of Insurance Medicine in 2008,

An important consideration [is] the extent to which each study (a) excluded persons with pre-existing medical conditions, perhaps those due to smoking, and (b) controlled for various co-morbid factors, such as age, sex, race, education, weight, cholesterol, blood pressure, heart disease, and cancer. Studies that excluded persons with medical conditions due to smoking, or controlled for factors related to smoking (e.g., blood pressure), would be expected to find lower RRs. Conversely, studies that did not account for sufficient confounding factors (such as age or weight) might find higher RRs.

So, which of these – or any other – effects of smoking is the writer alluding to? Quoting from the New Scientist article,

Lonely people are at increased risk of “just about every major chronic illness – heart attacks, neurodegenerative diseases, cancer,” says Cole. “Just a completely crazy range of bad disease risks seem to all coalesce around loneliness.” A meta-analysis of nearly 150 studies found that a poor quality of social relationships had the same negative effect on risk of death smoking, alcohol and other well-known factors such as inactivity and obesity. “Correcting for demographic factors, loneliness increases the odds of early mortality by 26 per cent,” says Cacioppo. “That’s about the same as living with chronic obesity.”

The metaphor the writer was going for was one of longevity. Bleh.

When I searched for the provenance of this comparison (between smoking and loneliness), I landed up on two articles by the British writer George Monbiot in The Guardian, both of which make the same claim*: that smoking 15 cigarettes a day will reduce your lifespan by as much as a lifetime of loneliness. Both claims referenced a paper titled ‘Social Relationships and Mortality Risk: A Meta-analytic Review’, published in July 2010. Its ‘Discussion’ section reads:

Data across 308,849 individuals, followed for an average of 7.5 years, indicate that individuals with adequate social relationships have a 50% greater likelihood of survival compared to those with poor or insufficient social relationships. The magnitude of this effect is comparable with quitting smoking and it exceeds many well-known risk factors for mortality (e.g., obesity, physical inactivity).

In this context, there’s no doubt that the writer is referring to the benefits of smoking cessation on lifespan. However, the number ’15’ itself is missing from its text. This is presumably because, as Cacioppo – one of the scientists quoted by the New Scientist – says, loneliness can decrease your lifespan by 26%, and I assume an older study cited by the one quoted above relates it to smoking 15 cigarettes a day. So I went looking, and (two hours later) couldn’t find anything.

I don’t mean to rubbish the congruence as a result, however – far from it. I want to highlight the principal reason I didn’t find a claim that fit the proverbial glove: most studies that seek to quantify smoking-related illnesses like to keep things as specific as possible, especially the cohort under consideration. This suggests that extrapolating the ’15 cigarettes a day’ benchmark into other contexts is not a good idea, especially when the writer does not know – and the reader is not aware of – the terms of the ’15 cigarettes’ claim nor the terms of the social relationships study. For example, one study I found involved the following:

The authors investigated the association between changes in smoking habits and mortality by pooling data from three large cohort studies conducted in Copenhagen, Denmark. The study included a total of 19,732 persons who had been examined between 1967 and 1988, with reexaminations at 5- to 10-year intervals and a mean follow-up of 15.5 years. Date of death and cause of death were obtained by record linkage with nationwide registers. By means of Cox proportional hazards models, heavy smokers (≥15 cigarettes/day) who reduced their daily tobacco intake by at least 50% without quitting between the first two examinations and participants who quit smoking were compared with persons who continued to smoke heavily.

… and it presents a table of table with various RRs. Perhaps something from there can be fished out by the New Scientist writer and used carefully to suggest the comparability between smoking-associated mortality rates and the corresponding effects of loneliness…

*The figure of ’15 cigarettes’ seems to appear in conjunction with a lot of claims about smoking as well as loneliness all over the web. It seems 15 a day is the line between light and heavy smoking.

Featured image credit: skeeze/pixabay.