Poly-tobacco product use among a representative sample of Chinese current smokers: a population survey


 BackgroundPoly-tobacco product use is increasingly popular, but little is known about the patterns, trends of concomitant use, and risk factors particularly in non-western countries.MethodA representative sample of 1139 current cigarette smokers aged 15+ (84.1% male) were telephone interviewed in Tobacco Control Policy-related Surveys in 2015-2017. Information collected included poly-tobacco use (PTU), smoking and socio-demographic characteristics. Associations of current PTU with related risk factors were analyzed using logistic regression with adjustment for confounders. Prevalence was weighted by age and sex of current cigarette users in the general population.Results 15.9% (95% CI 13.4-18.6%) were current poly-users, 12.3% (10.2-14.8%) used one tobacco product and 2.52% (1.59-3.97%) used two tobacco products in addition to cigarette. The co-use of cigarette with cigar was more common and the least co-use product was e-cigarette with cigarette. By age group, proportion of co-use of cigarette with waterpipe was highest in young poly-users, older age used more cigar and self-rolling cigarette in addition to cigarette. Prevalence of two products use with cigarette was low. Trends of concomitant use were varied. Current PTU was associated with being male (AOR 2.01, 95% CI 1.12-3.61), younger age (AORs range from 1.34-4.65, P for trend < .001) and less ready to quit (2.08, 1.09-3.97). ConclusionsPrevalence of PTU increased slowly by year, co-use of one tobacco product with cigarette was more common. Being male, younger and less ready to quit were associated with current PTU. [236/250 words]

Foreign and local tobacco companies have been rapidly expanding business in China targeting youth. 15 Hong Kong is the most westernized city of China with remarkably low cigarette smoking prevalence compared with other Asian regions (10% in 2017), 16 but the use of EC and waterpipe had increased in the past few years. [17][18] In Hong Kong, any sale promotions of tobacco products are prohibited, but marketing and purchasing via social media (e.g. Facebook and Instagram) are not strictly regulated by the government. 19 Many of these tobacco products are readily available for purchase in the Internet without age restriction. 20 Such grey area in regulations created a loophole for promotion and sale of alternative tobacco products for concomitant use.
We investigated the overall prevalence of PTU, patterns of concomitant use among current smokers, and examined the trends of PTU strati ed by patterns of concomitant use. We also identi ed the association of PTU with socio-demographic characteristics and modi able risk factors (Heaviness of Smoking Index and intention to quit smoking cigarette). . The telephone-based survey was conducted by the Public Opinion Program (POP), the University of Hong Kong. Residential telephone numbers were drawn randomly from residential telephone directories to become seed numbers, another set of numbers were generated using "plus/minus one/two" approach to capture unlisted numbers. One eligible person was selected among the eligible family members using the "next birthday" approach, whose birthday nearest to the survey date was selected at the time of interview. The respondents of the surveys included (1) current cigarette smokers, who smoked at least one cigarette in the past 7-day (N = 5113); (2) ex-smokers, who had abstained and reported no cigarette smoking in the past 7 days (N = 5141) and (3) never smokers (N = 5280). The whole sample of 15534 Cantonese-speaking participants was weighted by sex, age and smoking status using inverse probability weighting to make the sample more representative to Hong Kong population. 16 A representative sample of 1139 current cigarette users was analyzed. All respondents provided oral consent before the telephone interview. Ethical approval was sought from the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster.

Measurements
Baseline socio-demographic characteristics were collected, including sex, age, educational attainment, marital status, employment status (economically active and non-active) and monthly household income.
Nicotine dependence was measured by Heaviness of Smoking Index (HSI). 21 Respondents were asked about their intention to quit smoking (quit in 30-day vs quit after 30-day). 22 Current cigarette smokers reported using other tobacco products (cigars, self-rolling cigarette, waterpipe and electronic cigarette) within 30-day were categorized as current poly-users. PTU was categorized by number of tobacco products use (one tobacco product or two tobacco products use in addition to cigarette) and patterns of concomitant use.

Statistical analysis
Socio-demographic characteristics, prevalence of PTU and concomitant use were weighted by sex and age distribution of 2017 Hong Kong adult current cigarette users. The associations of socio-demographic characteristics, HSI and intention to quit with current PTU were analyzed using multivariable logistic regression, controlling for sex, age, educational attainment and monthly household income. Results were reported as adjusted odds ratio (AOR). All the analyses were performed using STATA (V. 13.0). Two-tailed p-value less than 5% is considered as statistically signi cant. Listwise deletion was used to handle missing value due to a small proportion of data was missing.
For socio-demographic characteristics variables, only sex and age were associated with current use of poly-tobacco product. Inverse association was found between age and current PTU; the AOR increased with younger age and the association remains strongly signi cant after adjustment. (P for trend less than 0.001). No intention to quit cigarette smoking was associated with current PTU (AOR 2.08, 95% CI 1.09-3.97). HSI was not associated with current PTU before and after adjustment.

Discussion
This is the rst large scale study to examine the prevalence of PTU, patterns and trends of concomitant use, and risk factors associated with PTU from a large representative sample of Chinese general population. We observed that the prevalence of current PTU (15.9%) was lower than the U.S. (38.7%), 23 but was higher than that in some large European countries, such as Russian (15.6%), Ukraine (12.0%) and Turkey (12.3%). 24 Studies from other countries (e.g. U.S., Canada and Egypt) also showed consistent ndings of increasing prevalence of PTU. [24][25] The increasing concomitant use may be driven by relatively strict regulation of cigarettes sales compared with alternative tobacco products. Small geographical area (e.g. Hong Kong) along with high penetration of smartphone also contributes to the increasing concomitant use via frequent expose to social media promotion on alternative tobacco products. 26 Estimates indicated using one tobacco product was more common than using two tobacco products in addition to cigarette (12.3% vs. 2.52%). Among this, cigar was the most used tobacco product (6.28%) compared with EC (1.05%). This suggested EC was less popular for concomitant use and those who used EC were more likely to be exclusive EC users. Dual use of cigar and cigarette was associated with less negative perception toward cigarette use and quit attempts, 27 tobacco intervention program speci c to this subgroup of smokers is warranted to prevent the growth of this type of co-use. We examined the patterns of concomitant use with cigarette over three years. Compared with dual use of waterpipe and cigarette, the prevalence of cigar or self-rolling cigarette with cigarette use dropped slightly in 2016, then raised in the next year. For two tobacco products use in addition to cigarette, only self-rolling cigarette with waterpipe use had steady increase by year. The varied patterns of concomitant use suggested these smoking behaviors had not been routinized. PTU is in the early stage of epidemic in Hong Kong, continuous monitoring and early intervention are warranted to prevent progression of longterm concomitant use.
Although studies on social norm and risk perception of PTU are limited, some studies had examined the socio-demographic characteristics associated with PTU. 11 28-29 Consistent with previous studies in other countries, 2 9 30-31 our ndings showed that being male and younger age were positively associated with current PTU. Men were reported with higher risk-taking and sensation-seeking behaviors, such as drug or alcohol abuse and smoking experimentation. 32-33 Dose-response relationship was observed between age and current PTU; being younger was signi cantly more likely to use multiple tobacco products in addition to cigarette. The association remains signi cant and robust after accounting for confounders. Tobacco industries mainly target young population by introducing these products (e.g. waterpipe) in different avors and promoting the products as less harmful than conventional cigarette on social media. 34 This age group of current smokers perceived PTU as less harmful, less addictive and more fashionable than smoking cigarettes. [35][36] Many of cigar and waterpipe lounges were also densely located in nightlife district, where the modern and luxurious environments attracted large amount of young smokers. 18 Our ndings highlighted that younger age was a signi cant risk factor for current PTU, further studies are needed to explore their knowledge and perception about concomitant use.
We extend the understanding of smoking and quitting behaviors with current PTU. Current smokers with no intention to quit conventional cigarette had higher odds of PTU. Other studies found positive association between higher quit attempts and PTU. 11 37 The results were explained by the nding that poly-users had lower intention to quit smoking cigarette because they experienced less cessation success despite with higher quit attempts. 22 Most of the poly-users were young and young smokers were associated with lower intention to quit smoking cigarette compared with other age groups. 12 38 Instead of complete abstinence from smoking cigarettes, young smokers switched from exclusive cigarette users to poly-users for smoking experimentation. 11 39 40 Some studies showed positive association between nicotine dependence and PTU, 8 12-14 this was inconsistent with our nding. Heaviness of Smoking Index only measured the degree of nicotine dependence from smoking cigarette, it is possible that current smokers who concomitantly used cigarette with other tobacco products did not solely rely on cigarette to acquire nicotine and therefore smoked less compared with exclusive cigarette smokers. Such behavior is a barrier for smoking cessation treatment, as this speci c group of smokers rarely seek cessation services and make them harder to quit. 37 Future longitudinal studies are needed to speci cally follow poly-users to investigate their smoking behaviors and cessation outcomes.
This study has some limitations. We were unable to determine the temporal relationships given the crosssectional design. Although reverse causation between socio-demographic characteristics (sex and age) and PTU are unlikely, longitudinal study is needed to further explore the temporal relations of smoking and quitting behaviors with PTU. As smoking is generally considered unacceptable in Chinese culture, respondents may subject to social desirability bias due to nature of the survey. Socially desirable responses were likely to occur in response to sensitive questions, such as number of cigarette smoked and tobacco products used, 41-42 therefore the prevalence may be underestimated. Con dentiality was assured before the interview began, but data collected from the lane line surveys were self-reported and answers might still subject to measurement and reporting bias due to underreporting, attenuation of associations were possible. 43

Conclusions
We identi ed the prevalence of PTU, patterns and trends of concomitant use, and risk factors associated with such use. We found the prevalence of PTU had been slowly increasing in three years, co-use of one tobacco product with cigarette was more common, and which cigar and cigarette has the highest prevalence compared with other patterns of concomitant use. Among poly-users, young adults preferred co-use of waterpipe and cigarette, cigar and self-rolling cigarette were more common for co-use in older age group in addition to cigarette. Being male and less ready to quit were associated with current PTU. Strong association of being younger age with current PTU was also observed. These important risk factors can be the indicators to identify speci c vulnerable groups for designing public health campaigns and control multiple tobacco products use in future. Author's contribution MPW, DYT and THL designed the study. MPW, DYT and YW collected the data. YW, SLC and MPW analyzed the data. SLC and MPW drafted the manuscript. All authors critically revised and approved the nal version of the manuscript.

Figure 1
Prevalence of current poly-tobacco product use by sex, 2015-17 (n=1139) Figure 2 Overall prevalence of current poly-tobacco product use by number of tobacco product use, 2015-17 (n=1139)