Discussion
At the time of preoperative assessment, 4.6% and 10.7% of patients reported having used HTPs and cigarettes in the past 30 days, respectively. Although the data were collected at one point during the preoperative visit, we retrospectively examined patients’ tobacco use behaviour to ascertain the total exposure to cigarette smoking and the temporal sequence of tobacco product use using questions that specified the type of tobacco product used, the time of initiation and quitting and the number of cigarettes smoked during lifetime. Among current tobacco product users, exclusive HTP users had a comparable prevalence of airway obstruction to that of exclusive cigarette smokers. Furthermore, current HTP use was significantly associated with an increased likelihood of airway obstruction (APR=1.42, vs never used HTPs) among former smokers (those who had stopped smoking cigarettes for >30 days); a stronger association (APR=1.96, vs never used HTPs) was observed when the analysis was restricted to long-time (≥5 years) cigarette quitters.
In this study, there were 92 current exclusive HTP users, and the majority (N=89) of them had previously smoked cigarettes; thus, they had switched from cigarettes to HTPs at some point. Among current tobacco product users, we found that current HTP-only users were at a comparable risk of airway obstruction to those who were exclusively smoking cigarettes. This result is not in line with previous tobacco industry-related studies suggesting that a complete switch to HTP could reduce the adverse health effects of cigarettes. It should be noted, however, that the association observed in this study may be biased by unmeasured factors. For instance, some patients with previously identified lung or other health problems may have switched from cigarettes to HTPs to continue tobacco use with a product they consider to be ‘healthier’, which may complicate the link between HTP use and health outcome measures. Continuing follow-up and longitudinal assessment will be important to elucidate the pathway underlying the use of HTPs and the development of airway obstruction in real-world settings.
Another important finding of this study was that among former cigarette smokers, current HTP users had a significantly increased risk of airway obstruction relative to those who had never used HTPs, and this association remained consistent when the analysis was restricted to long-time cigarette quitters. This suggests that switching from cigarette smoking to HTP use may still pose a significantly higher risk of airway obstruction compared with complete tobacco abstinence. Recent reviews and experimental studies on the effects of HTPs suggest that HTPs share a common pathway to pulmonary disease with conventional cigarettes and that HTPs may not be safer than cigarettes in terms of damage to respiratory systems.13 14 19 20 32 33 HTPs are often marketed as a ‘cleaner alternative to cigarettes’ or ‘reduced risk product’,34–36 which has successfully shaped a health-conscious image around HTPs leading the public to underestimate the potential harm of the product.37–39 Tobacco control efforts require targeted messages toward smokers and the wider public that the use of any form of tobacco is not free from harm, and thus strongly discouraged. Furthermore, a recent large-scale longitudinal analysis of Japanese adults suggests that the use of HTPs does not help current cigarette smokers quit and that HTPs even increase the risk of cigarette smoking relapse for former smokers, suggesting that HTPs should not be considered as a cessation aid.40 In clinical settings, given that airway obstruction and many other tobacco-induced diseases develop after long-lasting exposure, HTP use should be routinely screened along with conventional cigarettes and patients should be advised at any clinical visit to stop using all types of tobacco.
This study had several limitations. First, we were unable to establish the causal relationship between HTP use and airway obstruction because the data were collected at one point during the preoperative assessment. However, we retrospectively investigated patients’ lifetime cigarette smoking (pack-year) and duration of smoking cessation. This allowed the analysis to consider past cigarette smoking behaviour in assessing the presence of airway obstruction, particularly among long-term cigarette quitters. Second, tobacco use status in this study was self-reported or reported by a proxy and not confirmed by serological testing, making it susceptible to misrecall, social desirability bias and misinformation provided by a proxy. However, it’s essential to note that the reliability of self-reported tobacco use has been previously validated,41 and we implemented measures to minimise reporting errors by offering guidance from trained hospital staff. Third, the study lacked a specific target sample size due to continuous data collection from all eligible patients. Despite this, the collected sample was deemed sufficient for reliable findings, as demonstrated by consistent results in sensitivity analyses and focused subgroup analyses on former cigarette smokers with appropriate adjustments. However, the data resulted in a small number of patients for certain tobacco use subgroups; for instance, there was only one former HTP-only user and three current HTP-only users with no history of cigarette smoking. Related to this limitation, we were unable to assess the relationship between HTP use and known smoking-related postoperative outcomes such as impaired cardiovascular function, infection, delayed or impaired wound healing, intensive care unit admission and in-hospital mortality42 43 due to the paucity of such events. Fourth, being derived from cancer surgery patients at a single centre, the study is subject to potential biases and limited generalisability due to specific population selection. Caution is warranted in extrapolating findings to broader populations, considering the distinct nature of the patient with cancer population, characterised by older age and specific lifestyle factors. Continued and extended data collection involving multiple medical facilities is warranted to address these limitations.
To conclude, among patients with cancer scheduled for surgery, the prevalence of airway obstruction was comparable between current HTP-only users and cigarette-only smokers after adjusting for lifetime cigarette smoking. Current HTP use was significantly associated with an increased prevalence of airway obstruction among those who had quit cigarette smoking, and this was more evident among long-time (≥5 years) cigarette quitters. Caution is warranted when interpreting these results due to potential differences in characteristics between current HTP users and non-users that were not adjusted for in this study. Nevertheless, our findings suggest that HTP use can be a risk factor for airway obstruction even when individuals switch from smoking cigarettes. Further assessments to elucidate the pathways between HTP use and the development of airway obstruction and other long-term tobacco-related diseases are needed. In clinical settings, patients should be routinely screened for HTP use and advised to stop using all types of tobacco.