Changes in Smoking Habits and Behaviors Following the Introduction and Spread of Heated Tobacco Products in Japan and Its Effect on FEV1 Decline: A Longitudinal Cohort Study

Background Heated tobacco product (HTP) use in Japan has rapidly increased. Despite this rapid spread, little is known about the health effects of HTP use. We conducted a longitudinal cohort study to investigate the change in smoking habits following the spread of HTP use and its effect on forced expiratory volume in 1 second (FEV1) decline. Methods Participants consisted of a resident population (n = 2,612; mean age, 67.7 years) with FEV1 measurement in 2012–2014 and 2018–2019, and a worksite population (n = 722; mean age 49.3 years) without FEV1 data. Participants were categorized as combustible cigarette-only smokers, HTP-only users, dual users, past smokers, and never smokers. The association between smoking group and the change in smoking consumption over a mean 5.6 years was examined. Differences in annual FEV1 change between smoking groups were examined in the resident population. Results Prevalence of HTP-only and dual users in 2018–2019 was 0.8% and 0.6% in the resident population, and 5.0% and 1.9% in the worksite population, respectively. The overall number of tobacco products smoked/used increased in dual users compared to baseline, but not in others. Annual FEV1 decline in dual users tended to be greater than that in cigarette-only smokers (16; 95% confidence interval, −34 to 2 mL/year after full adjustment). Participants switching to HTP-only use 1.7 years before had a similar FEV1 decline as cigarette-only smokers. Conclusions HTP use, including dual use, is prevalent even in a rural region of Japan. Dual users appear to smoke/use tobacco products more and have a greater FEV1 decline. Tobacco policy should consider dual use as high-risk.


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Heated tobacco product (HTP) use is rapidly increasing in Japan. Sales of HTPs 33 commenced in 2014, ahead of the world, and 7.2% of Japanese men and 1.4% of women were 34 reported to be users in 2018, versus 22.0% of men and 7.5% of women who used combustible 35 cigarettes. 1 Most HTP users previously smoked combustible cigarettes. 2 This drastic change in 36 the smoking habits of Japanese following the spread of HTPs should be appropriately reflected 37 in tobacco control policies, including dual using. Given the now gradual adoption of HTPs in 38 other countries, 3 4 information on the effect of HTP spread will be valuable worldwide. 39 While some populations use HTP and combustible cigarettes concurrently, the actual 40 number of such dual users is unclear, as studies have produced conflicting data. JASTIS 5 6 and 41 ITC Japan 2 7 have shown that the majority of HTP users were concurrent cigarette smokers. On 42 the other hand, the Japanese National Health and Nutrition Survey has reported the opposite. 8 43 Therefore, providing data from an independent cohort study using face-to-face interviews 44 would be of great significance. Moreover, the smoking behavior of HTP users, including dual harmful effects of combustible cigarettes when used alone, the health effects of dual use should 53 also be considered. 54 Nevertheless, evaluation of the health effects of newly introduced smoking products 55 is challenging. Long-term evaluation is required to determine whether the increases in cancer, 56 cardiovascular disease, stroke and COPD seen with combustible cigarette smoking 12 can be 57 replicated with HTPs. However, an adverse effect of smoking that is consistently observed over 58 a relatively short period is a decrease in forced expiratory volume in one second (FEV1) 13 . To 59 our knowledge, studies of the effect of HTP use on FEV1 are scarce. 60 The Tsuruoka Metabolomics Cohort Study, a population-based cohort study in Japan, 61 has collected longitudinal data on smoking habits and FEV1 from baseline in 2012, before 62 HTPs were sold, to follow-up in 2018, after HTPs became popular. Here, we used these data 63 to investigate the change in smoking habits following the introduction and spread of HTPs, to  Table 1).

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The study was approved by the Medical Ethics Committee of the Keio University  containing insert of IQOS and glo is a stick, while Ploom TECH is a capsule. 2 The use of one 112 stick of IQOS or glo was considered equivalent to smoking one combustible cigarette. As for 113 Ploom TECH, a single use was defined as using the device for 10 minutes or less, since 114 smoking one cigarette typically lasts less than ten minutes. Respondents were asked how many 115 times a day they used their device based on this interpretation, and we assessed that single use 116 of Ploom TECH device was equivalent to smoking one cigarette. Smoking history was also 117 collected, namely age at starting and quitting smoking. Smoking habits were categorized into 118 the following five groups according to information from the follow-up survey: combustible 119 cigarette-only smokers, HTP-only users, dual users, past smokers, and never smokers. No 120 participant used electric nicotine delivery systems other than HTPs, such as e-cigarettes.

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Combustible cigarette-only smokers were identified as smokers who smoked at least one    Three models were used for this analysis. Model 1 was crude, model 2 was adjusted for sex 163 and age, and model 3 was adjusted for sex, age, height, FEV1 at baseline and the number of follow-up. In both populations, HTP only and dual users were younger than the other groups.

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HTP use was more frequent in the younger population (Table 3), and HTP users were    This study showed that HTP use was prevalent even in the rural area of Japan. Among 220 our participants, a prevalence of HTP use for men in the 40s, 50s, 60s, and 70s were 16.7%, 221 9.5%, 3.4%, and 0.4%, respectively, whereas for women, 2.6% in their 40s, 0.9% in the 50s, 222 and 0% in the 60s and 70s. These prevalence were similar to other surveys which likely were 223 heavily weighted towards urban areas. 1  indicating that participants likely misclassified these two new tobacco products, as noted by 239 the authors. Such misclassification of HTP use is a major concern and has not been sufficiently 240 addressed in the previous studies. 22 23

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Other surveys in Japan also showed a high proportion of dual users among HTP users 2 242 5-7 , while that of the Japan National Health and Nutrition Survey in 2018 was similar to or 243 slightly lower than our study. 8 This conflict may be due to differences in sampling methods and 244 questioning methods. In the Japan National Health and Nutrition Survey, random selection was 245 conducted nationwide, but the questionnaire was limited in that the section on HTP use was 246 not separated. Other nationwide surveys focused on HTP use, had detailed questionnaires on 247 HTP use, but were conducted mainly through internet surveys.

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The strength of this study is that misclassification was reduced as much as possible. 249 We asked product-specific questions about HTP use, separate from the questionnaire for  changing the habit of smoking. Further, our results also suggest that dual users tend to smoke 270 more than they did prior to initiating the use of HTPs. One likely explanation for this is that 271 HTP use might lead to a decrease in hesitation to smoke in public spaces, given that tobacco reported that urinary levels of nicotine metabolites after the six-month trial were closely 284 similar. 27 If so, it can be considered that HTP users compensate for the reduced nicotine by 285 using HTPs for longer or deeper than combustible cigarettes.

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Nicotine dependence was closely consistent between combustible cigarette smokers 287 and HTP-only users in this study. Switching to HTP use alone was not associated with nicotine 288 dependence. It is possible that dual users had higher nicotine dependence than other smokers 289 in the worksite population, but careful interpretation is needed because the sample size is small.

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Stages of behavioral change in quitting smoking did not differ among the three smoking groups.

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Only 5% of smokers were at the preparation stage, and most had little intention to quit, HTPs is markedly limited. Some toxic substances such as tobacco-specific nitrosamines and 303 polycyclic aromatic hydrocarbons are reportedly reduced in IQOS aerosol, whereas other 304 compounds such as formaldehyde and nicotine remain. 10 11 28 Given the paucity of evaluation, 305 it is not clear whether HTPs have fewer harmful effects than combustible cigarettes. A decline 306 in FEV1 has been established as a short-term effect of the adverse effect of smoking cigarettes. 13 307 29 This effect was also confirmed in our study. The annual decline in FEV1 among cigarette 308 only smokers were 13 mL/year higher than never smokers, and comparable to previous studies.

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The results of a systematic review of 47 studies on the annual decline in FEV1 due to smoking 310 showed that the annual decline in FEV1 was over 10 mL/year greater than in smokers compared 311 with non-smokers. 13 Although the sample size was small, our results showing that the decline           A c c e p t e d V e r s i o n