A Cochrane Review concluded that the effectiveness of heated tobacco use for smoking cessation remains uncertain. There was moderate‐certainty evidence that heated tobacco users have lower exposure to toxicants/carcinogens than cigarette smokers.
Eligible outcomes included in the review were smoking cessation, adverse events, and selected biomarkers, reports VapingPost.
There was a total of 13 completed studies, of which 11 were randomised controlled trials (RCTs) assessing safety (2,666 participants) and two were time‐series studies, however, given that all the RCTs included were funded by tobacco companies, possible bias was taken into account.
The researchers said there was moderate‐certainty evidence that heated tobacco users have lower exposure to toxicants/carcinogens than cigarette smokers and very low‐ to moderate‐certainty evidence of higher exposure than those attempting abstinence from all tobacco. They added that independent studies on the effectiveness and safety of the products are required.
Carbonyl emissions from from HTPs
A 2018 study conducted by anti-smoking expert Dr Konstantinos Farsalinos had analysed and compared carbonyl emissions from an HnB device, an e-cigarette and a regular cigarette.
Compared with the tobacco cigarettes, levels for HnB devices were found to be 91.6% lower for formaldehyde, 84.9% lower for acetaldehyde, 90.6% lower for acrolein, 89.0% lower for propionaldehyde and 95.3% lower for crotonaldehyde.
Regarding e-cigarettes, no levels of propionaldehyde and crotonaldehyde, and very low levels of the other carbonyls were detected. When using 5g of e-cigarette liquid, in comparison to 20 cigarettes, a 92.2 to 99.8% reduced level of carbonyls was noted. When comparing 20 heets sticks with the same amount of cigarettes, an 81.7 to 97.9% level of reduced emissions was measured.
HTPs vs cigarettes
Similarly, a 2020 study comparing the amount of carcinogens between regular cigarettes and heated tobacco products, found that the latter contain about 10- to 25-fold lower carcinogens than cigarettes.
Titled, “Method for Comparing the Impact on Carcinogenicity of Tobacco Products: A Case Study on Heated Tobacco Versus Cigarettes,” the study looked at eight carcinogens known to occur in the emissions of both heated tobacco products (HTPs) and tobacco smoke.
The researchers compared the harmful health effects of the two products by applying a risk assessment method of six steps. “The first three steps encompass dose-response analysis of cancer data, resulting in relative potency factors with confidence intervals.
The fourth step evaluates emission data, resulting in confidence intervals for the expected emission of each compound. The fifth step calculates the change in cumulative exposure (CCE), probabilistically, resulting in an uncertainty range for the CCE. The sixth step estimates the associated health impact by combining the CCE with relevant dose-response information.”
The compiled data indicated that CCE was estimated to be 10- to 25-fold lower when using HTPs instead of cigarettes. The researchers pointed out that this difference indicates a substantially smaller reduction in expected life span, based on available dose-response information in smokers. However, given that only eight carcinogens were considered, this is only a preliminary conclusion.
Study details
Heated tobacco products for smoking cessation and reducing smoking prevalence
Harry Tattan-Birch, Jamie Hartmann-Boyce, Loren Kock, Erikas Simonavicius, Leonie Brose, Sarah Jackson, Lion Shahab, Jamie Brown.
Background
Heated tobacco products (HTPs) are designed to heat tobacco to a high enough temperature to release aerosol, without burning it or producing smoke. They differ from e‐cigarettes because they heat tobacco leaf/sheet rather than a liquid. Companies who make HTPs claim they produce fewer harmful chemicals than conventional cigarettes. Some people report stopping smoking cigarettes entirely by switching to using HTPs, so clinicians need to know whether they are effective for this purpose and relatively safe. Also, to regulate HTPs appropriately, policymakers should understand their impact on health and on cigarette smoking prevalence.
Objectives
To evaluate the effectiveness and safety of HTPs for smoking cessation and the impact of HTPs on smoking prevalence.
Selection criteria
We included randomised controlled trials (RCTs) in which people who smoked cigarettes were randomised to switch to exclusive HTP use or a control condition. Eligible outcomes were smoking cessation, adverse events, and selected biomarkers. RCTs conducted in clinic or in an ambulatory setting were deemed eligible when assessing safety, including those randomising participants to exclusively use HTPs, smoke cigarettes, or attempt abstinence from all tobacco. Time‐series studies were also eligible for inclusion if they examined the population‐level impact of heated tobacco on smoking prevalence or cigarette sales as an indirect measure.
Data collection and analysis
We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking at the longest follow‐up point available, adverse events, serious adverse events, and changes in smoking prevalence or cigarette sales. Other outcomes included biomarkers of harm and exposure to toxicants/carcinogens (e.g. NNAL and carboxyhaemoglobin (COHb)). We used a random‐effects Mantel‐Haenszel model to calculate risk ratios (RR) with 95% confidence intervals (CIs) for dichotomous outcomes. For continuous outcomes, we calculated mean differences on the log‐transformed scale (LMD) with 95% CIs. We pooled data across studies using meta‐analysis where possible.
Main results
We included 13 completed studies, of which 11 were RCTs assessing safety (2666 participants) and two were time‐series studies. We judged eight RCTs to be at unclear risk of bias and three at high risk. All RCTs were funded by tobacco companies. Median length of follow‐up was 13 weeks. No studies reported smoking cessation outcomes.
There was insufficient evidence for a difference in risk of adverse events between smokers randomised to switch to heated tobacco or continue smoking cigarettes, limited by imprecision and risk of bias (RR 1.03, 95% CI 0.92 to 1.15; I2 = 0%; 6 studies, 1713 participants). There was insufficient evidence to determine whether risk of serious adverse events differed between groups due to very serious imprecision and risk of bias (RR 0.79, 95% CI 0.33 to 1.94; I2 = 0%; 4 studies, 1472 participants). There was moderate‐certainty evidence for lower NNAL and COHb at follow‐up in heated tobacco than cigarette smoking groups, limited by risk of bias (NNAL: LMD −0.81, 95% CI −1.07 to −0.55; I2 = 92%; 10 studies, 1959 participants; COHb: LMD −0.74, 95% CI −0.92 to −0.52; I2 = 96%; 9 studies, 1807 participants). Evidence for additional biomarkers of exposure are reported in the main body of the review.
There was insufficient evidence for a difference in risk of adverse events in smokers randomised to switch to heated tobacco or attempt abstinence from all tobacco, limited by risk of bias and imprecision (RR 1.12, 95% CI 0.86 to 1.46; I2 = 0%; 2 studies, 237 participants). Five studies reported that no serious adverse events occurred in either group (533 participants). There was moderate‐certainty evidence, limited by risk of bias, that urine concentrations of NNAL at follow‐up were higher in the heated tobacco use compared with abstinence group (LMD 0.50, 95% CI 0.34 to 0.66; I2 = 0%; 5 studies, 382 participants). In addition, there was very low‐certainty evidence, limited by risk of bias, inconsistency, and imprecision, for higher COHb in the heated tobacco use compared with abstinence group for intention‐to‐treat analyses (LMD 0.69, 95% CI 0.07 to 1.31; 3 studies, 212 participants), but lower COHb in per‐protocol analyses (LMD −0.32, 95% CI −1.04 to 0.39; 2 studies, 170 participants). Evidence concerning additional biomarkers is reported in the main body of the review.
Data from two time‐series studies showed that the rate of decline in cigarette sales accelerated following the introduction of heated tobacco to market in Japan. This evidence was of very low‐certainty as there was risk of bias, including possible confounding, and cigarette sales are an indirect measure of smoking prevalence.
Conclusions
No studies reported on cigarette smoking cessation, so the effectiveness of heated tobacco for this purpose remains uncertain. There was insufficient evidence for differences in risk of adverse or serious adverse events between people randomised to switch to heated tobacco, smoke cigarettes, or attempt tobacco abstinence in the short‐term. There was moderate‐certainty evidence that heated tobacco users have lower exposure to toxicants/carcinogens than cigarette smokers and very low‐ to moderate‐certainty evidence of higher exposure than those attempting abstinence from all tobacco. Independently funded research on the effectiveness and safety of HTPs is needed. The rate of decline in cigarette sales accelerated after the introduction of heated tobacco to market in Japan but, as data were observational, it is possible other factors caused these changes. Moreover, falls in cigarette sales may not translate to declining smoking prevalence, and changes in Japan may not generalise elsewhere. To clarify the impact of rising heated tobacco use on smoking prevalence, there is a need for time‐series studies that examine this association.
2018 Vapingtpost article – Comparing Emissions from HnBs, E-Cigs and Cigarettes (Open access)
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Switch to heated tobacco from cigarettes may reduce toxic exposure – Cochrane Review
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