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Replication is necessary to determine whether the recent critical meta-analysis of heated tobacco studies holds water.
The meta-analysis was generally down on both the reduced risk potential of heated tobacco products (HTPs) and their ability to function as smoking-cessation aids. The general opinion of the results from those in the reduced-risk health space was that they were certainly interesting but that further work should be done on both the issues that were studied in the individual works of research making up the meta-analysis as well as the meta-analysis itself.
If HTPs are both not as reduced in risk profile from conventional cigarettes and not as effective as substitution tools for cessation, then other studies should be able to replicate both points as time progresses and more research in the area of HTPs is conducted.
There is a feeling – from both pro- and anti-HTP viewpoints – that HTP research has been somewhat ignored. This could be a contributing factor to why so much of the HTP research currently published is directly backed by industry funding. If non-industry researchers have been interested in HTP research – or able to find funding to support it – there would be more non-industry-backed examinations of HTP claims. Instead, it may be that hysteria over vaping has drawn much of the interest (and, therefore, the money) over the past few years. This may start to change as restrictions on vaping continue to grow and other products such as HTPs and nicotine pouches increase in popularity.
Not glamorous, but necessary
There are other studies and meta-analyses being performed outside of the industry in the area of HTP research. One example is that researchers from the National Autonomous University of Mexico (UNAM) and the University of Catania, in Italy, recently performed an extensive review of 17 independent and industry-funded studies that looked at carbonyls in aerosol emissions with special focus on reproducibility of experiments, appropriate analytic methods and puffing regimes.
The researchers said: “Most revised studies complied with these requirements, but some were unreproducible, while others failed to consider analytical variables that may have affected the results and/or produced unrealistic comparisons. The outcomes from the revised studies and regulatory evaluations tend to agree with and converge to a general consensus that HTP aerosols expose users to significantly lower levels of toxicity than tobacco smoke.”
Further replication of research would also reduce worries about the studies that are fed into meta-analyses. Much like training artificial intelligence systems, the robustness of the final outcome depends entirely on the suitability of the feed material – if rubbish goes in, rubbish will come out.
Replicating existing work in the HTP/conventional tobacco space would allay some worries that flawed or inconsistent data will lead to unreliable conclusions. But replication is a major problem that touches on many areas of scientific research. In essence, it’s neither sexy nor profitable to replicate existing studies. All the interest and all the money is in forging new ground.
Several funds have been set up specifically to address this. In tobacco control, there is the Replica Project funded by Global Action to End Smoking (formerly Foundation for a Smoke-free World, FSFW). That, of course, is in itself its own problem, with many continuing to maintain that funds from Global Action are industry-tainted due to the large endowment given to FSFW at its inception by Philip Morris International. That makes that a crisis within a crisis with both industry influence and replicability issues layered together.
Issues with comparisons and criticisms
Outside replicability, some further questions were asked of the critical meta-analysis. For one, it was unclear why some some studies were not picked up by the meta-analysis investigation. Researchers were also critical of the lack of long-term studies and the fact that most compared HTPs to conventional cigarettes with few attempting to compare different reduced-risk products against each other. The former will hopefully be addressed in the fullness of time with more longer-term and longitudinal studies of HTPs being added to the existing body of research.
The latter may also be more of a time issue than anything else. Presumably, studies currently focus on HTPs versus conventional cigarettes, as cigarettes are the real public health threat. But as the number of smokers continues to decrease, it will become more pressing, and more interesting, to compare those products on the reduced-risk spectrum against each other as researchers look for the best overall public health outcome.
Meanwhile, the researchers behind the meta-analysis were also critical of the wide use of laboratory settings in research on HTPs, saying actions taken in such areas may not match real-life usage. Instead, the use of real-world evidence (RWE) would potentially be a more realistic data set for assessing health and cessation impact of HTPs.
But it was only recently that studies on vaping were criticised for not being conducted in controlled trial settings and relying on RWE to demonstrate the cessation potential of vaping technology. The thought pattern then was similar, though running in the opposite direction. Utilising RWE was not as effective, as any cessation benefits demonstrated could not be shown to be solely attributed to vaping and could be due to a variety of other factors that would be limited in controlled settings. It seems odd to now be criticising HTP research for concentrating primarily on controlled settings and ignoring the potential changes in behaviour and results that usage in real-life settings may bring about.
Broadening studies for optimal results
The researchers behind the meta-analysis also criticised HTP research for focusing generally on exposure to harmful chemicals rather than actual health effects or health changes in the body. This again, some suggested, was an odd criticism given that establishing causation between HTPs and health effects or changes in the body is significantly more difficult than proving a link between what would be first steps – HTPs and changes in exposure to harmful chemicals (with the assumption that any such increases or decreases would likely then lead to changes in health effects or the body itself).
Regardless, any future meta-analyses will have at least one more study looking at a link between HTPs and actual health effects. A newly published study looking at smokers switching to vaping or HTPs showed significant improvements in aerobic capacity after quitting conventional cigarettes.
An interesting aspect was that the study looked at smokers who quit completely as well as those who significantly reduced conventional cigarette use but still dual-used, while also comparing the effects of HTPs and vaping.
It found clinically meaningful improvements for both quitter and reducer (dual use) groups in a potential small counterpoint to the meta-analysis which did not find much improvement from those who cut back but did not quit smoking entirely when switching to HTPs. It also compared vaping versus HTPs but did not find a significant difference between the use of the two in terms of improvements in aerobic performance.
The study examined 220 smokers divided evenly into two groups given vaping products or HTPs for 12 weeks, though only 187 ended up being available for secondary analysis. Out of those, 67 quit smoking, 88 reduced (with on average more than a 75% reduction in cigarette consumption) and 32 did neither.
Further work such as this could make an impact on any future meta-analyses – if the results are replicated elsewhere.
– Freddie Dawson TobaccoIntelligence senior contributing editor
Image: AI-generated
