Waterpipe smoking among university students in Hong Kong: a cross-sectional study

A cross-sectional survey was conducted. All eight public universities funded by the University Grants Committee and form the major higher education institutions in HK were invited to collaborate with the study. One university declined the invitation due to their academic schedule. Each of the remaining seven universities’ Student Affairs or related administration department was asked to send the survey website link to enrolled students through registered student emails. This was sent as one bulk email to all students (total around 126,549 students, according to the universities’ reports) in April 2018 to reduce the burden of multiple bulk emails. The invitation email included general information about this study, such as details about the aim and incentive (i.e., Five participants randomly selected through lucky draw would receive HK$500 each [US$ 1 = HK$ 7.82] as a participation incentive). The participant inclusion criteria were: 1) currently registered as a student in a HK public university, 2) current HK resident, 3) English-speaking (main language of instruction in HK universities). The exclusion criteria were: 1) aged 17 years or younger, and 2) overseas exchange students.

Five thousand two hundred forty-three students visited the survey introduction website, and 1288 university students (331, 280, 247, 156, 105, 92, and 77 students from each university respectively) went on to participate in the survey after reading and agreeing to the consent form (response rate among all website visitors: 24.6%).

Descriptive statistics were reported in proportions or means and standard deviations (SD). Median and interquartile ranges (IQR) were presented for skewed data. In those that reported trying WPS at least once (i.e., ever-users of waterpipe), descriptive characteristics of WPS behaviour were reported (i.e., patterns of WPS). To clarify differences between smoking behaviours, demographic and other descriptive statistics were compared between four smoking behaviour groups (never smoked, only ever smoked waterpipe, only ever smoked cigarettes, and ever smoked both cigarettes and waterpipe). Logistic regression yielded odd ratios (OR) and adjusted OR (aOR) for WPS (a binary variable). Multinomial logistic regression yielded risk ratios (RR) and adjusted RR (aRR) for four different smoking behaviours in relation to respondents’ characteristics. As WPS risk factors differed by gender in existing studies [11], we added interaction terms to test if gender modifies the association of alcohol consumption and psychosocial factors (i.e., SSB and loneliness) with ever use of waterpipe. Sensitivity analysis was also conducted through multiple imputation using chained equation to handle missing values [31].

This research reported that the prevalence of ever-WPS was 23.8%, while the prevalence of ever-tobacco smoking (i.e., WPS and/or CS) was 32.0% among the respondents in HK. The ever-WPS prevalence in United States (US) studies ranged between 15.1 and 41% (mean: 30.3%) among university students [11] and 3 and 44% (mean 18.2%) among youth - defined by the United Nations as persons aged 15–24 years [9]. In some Middle Eastern countries like Iran, where WPS is more socially acceptable than in other regions, ever-WPS prevalence rates were higher than that of US studies (42.5% in Iran) [32]. Although the prevalence of WPS among university students in US was slightly higher than that of HK, WPS in the US was the second most popular form of smoking after CS [11]. In contrast, we reported that the prevalence of ever-WPS was higher than the ever-CS prevalence (21.1%: cigarette-only smoking 8.2% and dual smoking 12.9%), which is similar to the rates commonly reported in Middle Eastern studies such as Lebanon [33], Jordan [34] and Syria [35]. Due to governmental and social efforts toward tobacco control, HK achieved the lowest daily CS prevalence ever (10.0%) in 2017 [36], and has one of lowest prevalences of CS in the world [37]. However, WPS control has received less attention, and tobacco control counterparts have been less aware of the popularity of WPS as an alternative to CS in HK [16]. Such conditions result in a higher WPS prevalence than CS among university students in HK.

Female CS prevalence in HK has consistently been lower than most developed Western countries [37]. Li, et al. [38] attributed this to the strong social bias regarding female smokers in HK. We also identified that females are negatively associated with cigarette-only smoking. Being female, however, was positively associated with waterpipe smoking. It is also contrary to the existing WPS studies in both Western and Middle East countries that reported male students being more likely to smoke waterpipe than female students in the same countries [11, 32, 39]. It can be deduced that different social circumstances and dynamics surrounding WPS and CS (e.g., social acceptance of female WPS) would influence female WPS prevalence. Qualitative approaches will be required to identify the dynamics that are absent in the current knowledge base.

Socialisation was identified as the top reason for WPS in US (56%) and Iran (65.3%) studies [40, 41]. In this study, the major motives for WPS were generally similar to the above studies, namely socialisation (82.7%). It was also established that WPS is a social activity as a significant number of waterpipe users smoked waterpipe with others. An Iranian study demonstrated that university students smoked waterpipe with not only their friends (63%), but also siblings (61.9%) and parents (58.4%) [32]. The students in HK, however, had mostly smoked waterpipe with their friends or acquaintances (96.7%), rather than with their family (3.3%) to seek socialisation. Chinese culture is more collectivistic than their more individualistic Western counterparts [42]. In a collectivistic culture, engaging in a group activity plays an important part to one’s relationships with others within the group and their sense of belonging to the group [43]. This can be interpreted to indicate that HK students would more strongly seek membership within a peer group they are already affiliated to due to the collectivistic culture in HK. Additionally, according to collectivistic cultural values and the importance of social hierarchy, they would be reluctant to smoke WPS with their family members because they (particularly female waterpipe smokers) believe that smoking with their parents or with persons of higher social positions would be immoral and impudent [44, 45].

Similar to another study [46], we identified that cigarette users were positively associated with a perceived loneliness level. However, the ever-WPS group reported a negative association with loneliness level and the waterpipe-only group presented the lowest proportion of loneliness in this research. Primack, et al. [47] found that WPS was less associated with mental health problems (e.g., depression and anxiety) than CS. As such waterpipe smokers may feel less lonely than cigarette smokers because WPS is a social activity. We also identified that all smoking forms had positive associations with SSB, but that dual smokers showed the highest SSB. Heinz, et al. [5] asserted that one SSB is often related to other SSBs. WPS studies [17, 32, 39, 48, 49] found that WPS is significantly associated with CS or cigarette smoking susceptibility, as one tobacco smoking behaviour can be the gateway to smoking other types of tobacco. As the initiation age of cigarette smoking (i.e., 18.8 years) was earlier than waterpipe smoking (i.e., 20.5 years) in the dual smoking group in this study (Table 4), CS may play a gateway role in WPS. Further research is required to examine the relationship, however.

In addition to CS, a study reported that alcohol consumption was associated with WPS [39]. This is in parallel with a finding from this research, that the majority of ever-waterpipe smokers reported that they tended to smoke waterpipe while also drinking alcohol. The most popular sites for WPS among the ever-waterpipe users in HK were bars (regular bars: 66.3% and waterpipe bars: 57.3%). Particularly, waterpipe-only users showed much higher associations with alcohol consumption than those in the cigarette-only group. Existing studies indicated that the combination of CS with alcohol drinking will lead to increased risk of brain damage and increased mortality rate [50‐54]. As waterpipe smoke contains as many toxins, it can be deduced that WPS with alcohol drinking may have a similar or more serious health impact than CS with alcohol drinking. However, to date, only a few studies have explored the relationship between WPS and alcohol consumption. Further WPS studies that focus on alcohol drinking are also recommended.

In HK bars, including those specialising in waterpipe, customers must order at least one item from the food and beverage menu in addition to the waterpipe. Therefore, the total cost of a WPS session is usually higher than the cost of a single waterpipe. We found that most ever-waterpipe smokers spent HK$200 (approximately US$26) or more for a single WPS session, which is more expensive than one pack of cigarettes (e.g., 1 pack of Marlboro cigarettes = HK$59) and considerably expensive for students. Corresponding to this, we also found that a high household income (HK$50,000 or above) was more positively associated with WPS (i.e., ever-waterpipe and waterpipe-only user groups). Conversely, high household income was negatively associated with the cigarette-only user group. However, a US study [11] argued that WPS is relatively inexpensive, which can be attributed to the difference in patterns of WPS between HK and other counties. Lipkus, et al. [6] reported that university students in the US typically smoked waterpipe at home or in student accommodations (46.4%), while only 5.2 and 6.5% of the HK students in this research smoked waterpipe at their own or others’ homes, respectively. As HK students mostly smoked waterpipe at bars or restaurants, they get charged per session and inevitably spend more money than US students.

Lastly, 96% of the respondents of this research who had ever smoked waterpipe in this research perceived the addiction risk of WPS positively. They were also confident about their ability to stop WPS as they wished. A literature review [18] reported that high proportions of waterpipe smokers in universities in both the Middle Eastern and Western countries (ranging between 79 and 98%) were highly confident about stopping WPS at any time they want, which is similar to the finding in this research. However, WPS is actually associated with a high risk of addiction [55], due to highly-addictive substances like nicotine in waterpipe tobacco and smoke [56, 57]. Despite the smokers’ confidence in being free from WPS addiction, they are undoubtedly exposed to a high chance of addiction.

We have discovered that HK is not free from the global popularity of WPS (23.8% waterpipe ever smoking among HK university students). Thus, there is an urgent need to monitor and control the WPS trend within the HK population.

As most students initiated WPS during their university education (mean age: 20.2 years), WPS prevention education including education on WPS health risks should be developed and delivered to the students upon entry to university or at pre-university level. Moreover, given the association of WPS with CS and alcohol drinking, the existing CS and alcohol drinking prevention and cessation programme will need to be reviewed to include further information on the compounded health risks with the addition of WPS.

We also identified that bars were the most popular place for WPS. Particularly, the popularity and demand of waterpipe in HK can be inferred, as students can easily smoke waterpipe in mainstream bars in addition to waterpipe bars in HK. However, specific regulations for WPS in the bars are absent in HK and many other countries [1]. More seriously, most bars in HK allow indoor WPS, although it is illegal. Due to the indoor WPS, waterpipe smokers and staff in the bars are exposed to serious health conditions due to first-, second-, and third-hand smoking. Hence, the government’s surveillance of indoor WPS should be reinforced.

This research has several limitations. We adopted a cross-sectional survey; hence, causality should not accordingly be inferred in the results. We recruited participants from 7 universities in HK, but the participants were not necessarily a representative sample of university students or all young adults. We conducted an online survey by sending a bulk invitation to the students’ university email accounts. This method can cause the issue of multiple responses from one participant. To address multiple responses, we collected the first four digits of each respondent’s national identification number. Moreover, sampling bias can be caused by the online survey method. Therefore, further studies recruiting more representative sample participants from the same population as this study will be useful to warrant our findings [58]. The results were based on participants’ self-report, which would be subject to social desirability and recall biases. Despite these limitations, the findings of this research will provide important information regarding the WPS situation in East Asia to guide further WPS studies.