A total of 14 studies met the eligibility criteria and were included in this review. Table 1 and 2 describes the characteristics and findings from the studies. These studies were heterogeneous involving both qualitative and quantitative methodologies with varying study designs to capture the information on the oral cancer risk-related knowledge, attitudes, and practices of South Asian immigrants in developed countries. The studies were conducted across four countries namely, United Kingdom (UK; n = 7), United States of America (USA; n = 5), Italy (n = 1), New Zealand (NZ; n = 1). Table 1 shows the salient features of the studies included in this review. The sample size (see Table 1 for study characteristics) of the studies ranged from 10 to 1618 participants with a total of 4224 in number. Participants were immigrants mainly from India, Pakistan and Bangladesh and consisted of first to third generations. The age of the participants ranged from 12-87 years and consisted of mostly males [20-22, 24-28, 38]. Eight of the studies addressed all the themes of the oral cancer risk-related knowledge, attitudes and practices among South Asians in developed countries [21, 24-28, 38, 39]. One quantitative study  mentioned use of validated questionnaire while three other quantitative studies [26, 27, 39] reported use of previously pilot-tested survey. One qualitative study described the data analysis process in detail with a view to address the rigour in study. The remaining studies did not provide any clear information in this area. The quality of the studies was rated as good (n=2) (score ≥ 80), fair (n=10) (score 50–79%) and poor (n=2) (score < 50%) (see Table 2 for study findings and quality rating).
The findings of this review were categorised under themes of Oral cancer knowledge, Oral cancer attitudes and Oral cancer practices which are explained below:
Theme 1: Oral cancer knowledge
Thirteen studies [20-22, 24-28, 38-42] explored the knowledge of South Asian immigrants regarding the oral cancer risk. These studies assessed the level of information as well as awareness of the participants in relation to the risk of oral cancer associated with the consumption of alcohol, tobacco and areca nut preparations. Most of the studies reported a general lack of knowledge (50%-76%) regarding oral cancer risk across respondents from South Asian subgroups irrespective of the native country, age, gender and social class [21, 25-28, 39, 40]. Shetty et al. indicated in a survey that there were many misconceptions among participants regarding possible causes of oral cancer including the use of oral contraceptives, removal of teeth and eating sugary food . In contrast, a few studies did show that participants had knowledge (58%-69%) about one or more risk factors responsible for causing oral cancer like smoking, alcohol use and guthka chewing [24, 38, 42]. This information was more common among more educated and second-generation individuals especially males [24, 38, 42]. Sources of knowledge among participants included school/college education, press or media, relatives (27%-43%), health education leaflets/awareness campaigns (24%-57%), dentists (16%-33%) [28, 40, 42].
Four studies also showed that even if respondents were aware of the harmful effects of chewing tobacco and alcohol use, there was scepticism regarding the association of pan/guthka with oral cancer [20, 22, 25, 41]. Similar qualitative findings were reported by Lokhande et al , Hrywna et al  and Banerjee et al  as they found mixed understandings prevalent among participants regarding oral cancer risk:
“There is a mixture of happiness and sadness, but I sometimes feel sad and very low. . . I think there is ‘‘100% health risk’’ to chew tobacco which can cause mouth disease.” (page 48) 
“I think supari is the most popular, that's not on the [survey]…. When I was younger I never even knew it was tobacco…I might have even put one in my mouth because I didn't know. It didn't even taste that bad from my memory. I would say supari and gutkha.” (page 5) 
A survey conducted in the UK concluded that respondents of Pakistani (69%) and Bangladeshi (85%) origin were more likely to have ‘low knowledge’ of oral cancer risk when compared to those of Indian (47%) ethnicity . However, Bangladeshi immigrants (66%) were found more likely to identify ‘pan’ as a possible cause of oral cancer than Indian-Gujarati (48%) immigrants in the USA . The adequate knowledge regarding oral cancer risk was also associated with religion, as Sikh participants were found less aware of oral cancer risk factors when compared to Muslim and Hindu participants [24, 28].
Theme 2: Oral cancer attitudes
The attitudes of South Asian immigrants towards oral cancer risk were reported in eight studies [20-22, 24-28, 38-43]. The relevant attitude items mainly were related to beliefs regarding the association of risk products with oral cancer, perceived benefits as well as harms of oral cancer risk practices and the context of the use of these risk substances. Some of the studies highlighted that the overall attitude of participants towards oral cancer risk was negative and unfavourable [25, 26, 39]. Poor beliefs were reported among participants (17%-41%) regarding preventive health behaviours and modification of risk practices [24, 26, 27, 39].
Four studies [25, 26, 39] found that people perceived betel quid/pan/guthka chewing habit good for their health (12%-43.6%) which makes ‘teeth and gum stronger’ and believed that it helps them to reduce stress (11.6%-51%), relieve boredom with refreshing feeling (22%-44%). These findings were reiterated by participants in the qualitative studies by Hrywna et al  and Banerjee et al :
“It has benefit; it can be therapeutic too sometimes,” (page 7) 
‘‘And there are people who feel good; they think it releases tension/worries. So sometimes I think that having a little can cool your mood if you are feeling angry or annoyed.’’
(page 535) 
Other specific health benefits of betel quid/pan/guthka perceived by participants included aiding in digestion (11%- 33.6%) and pain relief (6%-34.1%) [21, 25, 26, 39]. Furthermore, some studies found that use of pan/guthka was also encouraged among South Asians due to its fragrant smell (12.6%) , pleasant taste (35%-37.4%) [25, 26, 38, 39] and cosmetically appealing red staining on lips [26, 39]. Some people were found consuming betel nut preparations just out of habit and for refreshment (3.3% to 42.7%) [25, 26, 38, 39]. Similar views were highlighted in the qualitative studies [20, 41]:
“I find the smell of it very pleasant when I chew it. When someone else eats, I am attracted to the smell. That’s why I eat it.’’ (page 535) 
“To feel good or get a buzz. I'm sure that's why people use it.” (page 7) 
Respondents perceived few harms associated with betel nut products like dental problems, chest pain, hypertension and kidney stones [27, 38].
Some studies revealed wide cultural acceptability of betel nut products during festivals celebrations and special occasions (7.1%-18.2%) [24, 25, 38]. The use of tobacco-related products such as hookah, pan, and supari were found common at social gatherings or after meals [38, 41]. Moreover, people believed that society played an important role in influencing their habits [20, 22, 41] and it was hard to refuse offers of these products :
“My friends chew it and I cannot say no to them when they offer – it is rude to say no in our culture. . . Every third person in Pakistan chews tobacco.” (page 48) 
“I think paan is always a tradition at parties and weddings. A lot of these chewing things like supari and gutkha, I've seen when I was in India… the older men, after they eat their food or if they're going on a walk they just pack a lip….” (page 6) 
One study in the USA found the use of tobacco and betel preparations among older South Asians helped them connect to their homeland .
“...If you go to Jersey City or Iselin [cities in New Jersey with large South Asian populations], you'll see it's something that's so deeply rooted in their culture that it’s ok for us to do it. It justifies everything.” (page 7) 
Theme 3: Oral cancer practices
All studies [20-22, 24-28, 38-42, 44] explored the aspects of oral cancer risk related practices and reasons behind the initiation of these habits among South Asian immigrants. Up to 50% of participants were found engaged in one or more negative oral cancer risk related practices like smoking, alcohol drinking, chewing of betel quid and tobacco [20, 22, 24-28, 39, 43]. Pan/Betel quid chewing was revealed as the most popular practice (40%-97%) followed by smoking and guthka chewing [25, 26, 39]. Followers of Islam (8%-23%) were found less likely to consume alcohol when compared to Sikh (43%-100%) and Hindu communities (27.6%-64%) [24, 28], Whereas, betel nut and pan use were found more common among Muslim participants (24%-69%) along with Hindu (32%-71%) and Sikh participants (0%-95%) [24, 28, 42].
There were also notable age variations when the risk habits were initiated in their home countries ranging from 3-18 years [20, 21, 26, 39]. Various reasons were cited behind the initiation of these practices such as social networks made up of South Asian friends or co-workers (45%-48.2%), passing of habit from one generation to the next (3.3%- 81%), observation and encouragement within family members (27.5%- 81%) [21, 25, 26, 38, 43]. These findings were also reflected in the qualitative studies [20, 22, 41] as indicated in the quote below:
‘‘From observing. Mother would have it. Grandmother would have it. Aunts use it. When everyone would have it, I would have it too. To see what it’s like.’’ (page 535) 
“I must have influenced my son to get addicted to chew tobacco.” (page 48) 
Despite legal restrictions in developed countries, the easy availability of guthka/customisable pan in Asian grocery stores, restaurants, specialised pan stalls, and supermarkets was highlighted as a factor responsible for the continuation of risk practices among respondents [20, 22, 38]. Similar views were raised in focus groups by Banerjee et al. :
‘‘One of my brothers here said that it can be found in Pakistani...I mean Indian and Bangladeshi stores. Other stores don’t sell it, it’s true. Meaning...it is used by Bangladeshi and Indians as well...If some- one says it is restricted, I won’t agree. Not so much.’’ (page 534) 
A pilot study  in the USA revealed that immigration can also influence the patterns of risk practices with participants switching habits from pan chewing to guthka use (nearly 54%) due to the social unacceptability of the former and ease of procurement /storage of the latter. Supporting this notion is a study in the USA that found that people preferred smoking and sometimes swallowing the tobacco/pan instead of spitting it out because of society finding this inappropriate . However, some studies found that betel quid usage along with tobacco chewing/smoking was an integral part of lifestyles, deeply rooted in the culture of south Asians and that these practices simply continued in new settlements as a habit or addiction [25, 26, 38, 41, 43].
Studies also explored different actions and perspectives of South Asian immigrants on quitting oral cancer risk-related practices and found a general interest among respondents (30%-80%) in quitting their risk practices [25, 26, 28, 38, 39]. However, quitting these practices was acknowledged to be difficult among users (18.2%- 38%) [25, 26, 28, 38] who attempted to quit. Participants highlighted the role of self-motivation [20, 22], doctor/dentist [20, 24, 27, 38, 39, 42] as well as government checks [20, 22] in curtailing their use of tobacco/pan products. However, participants did not regularly see a dental 4%- 58%) when compared to general medical practitioners [24, 27, 39]. Furthermore, general practitioners were found to usually lack knowledge about gutkha/pan use among South Asians [20, 38] and hence rarely discussed the ill-effects of these products during the consultation [20, 27, 38, 39]. Similar findings were reported by Banerjee et al.  in their qualitative study:
‘‘Now that we go to the doctor, doctor asks do you smoke, do you drink. That’s all, not more than that. But they don’t say that you should not touch this at all. They don’t say that.’’ (page 537)