This is the first 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 findings 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 specific 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 long-term 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 findings 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 significantly more likely to use multiple tobacco products in addition to cigarette. The association remains significant and robust after accounting for confounders. Tobacco industries mainly target young population by introducing these products (e.g. waterpipe) in different flavors 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 findings highlighted that younger age was a significant 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 finding 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 finding. 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 specific group of smokers rarely seek cessation services and make them harder to quit. 37 Future longitudinal studies are needed to specifically 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 cross-sectional 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. Confidentiality 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