Smokeless tobacco: current use among Bangladeshi adolescents and association with increased oral cancer risk among Bangladeshi adults

A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophy.Background: Smokeless tobacco (SLT) use is a major public health burden and highly prevalent in Bangladesh. Over 20 million Bangladeshi adults are currently using SLT. Bangladesh Government had announced its vision to become a tobacco free country by 2040. Therefore, public health efforts focusing on preventing SLT onset among adolescents would contribute towards this vision. However, apart from national adolescent SLT prevalence from Global youth Tobacco Survey (GYTS), no other information linked to adolescent SLT use is available to inform future interventions. Also, SLT use related health burden such as oral cancer is highly prevalent in Bangladesh. Globally, Bangladesh ranked third for oral cancer related death. Every year over 8,000 Bangladeshi adults lost their lives because of this deadly disease. Regarding the relationship between SLT and oral cancer risk, there is a disconnection between the study findings from the western countries and developing countries. With the diversity of SLT products and its content there is a need to produce local evidence. Therefore, the overall aim of this PhD research was to examine the factors contributing to adolescent SLT use in Bangladesh and the role of SLT in oral carcinogenesis among Bangladeshi adults. Methods: To attain the study objectives, in 2015 a cross-sectional survey (n=790, response rate 100%) in two rural secondary schools and a hospital-based case-control study (n=507; case:169 and controls: 338, case participation rate 92.86%) were carried out in Bangladesh. Results: The findings of the adolescent cross-sectional survey suggest that the ever and current SLT prevalence among rural Bangladeshi adolescent was 9.5% (75) and 3.7% (29) respectively. Males were the leading users of SLT. Zarda (80%) is the most common type of SLT used by the adolescents. Rural Bangladeshi adolescent started using SLT as early as seven years old and younger. Social sources (41.4%) were the most common source of SLT reported. Most adolescents (65.2%) were able to buy SLT from commercial stores without any restrictions. Many current SLT users (89.7%) wanted to quit SLT but professional help was not available. Overall, adolescents had good knowledge about the adverse effects of SLT use, though misconceptions about the addictive nature of SLT use were prevalent. Older age, self-efficacy, perceived barriers, perceived benefits and perceived severity were the significant predictors of adolescent SLT use. The findings of the hospital-based case-control study suggest a strong association between SLT use and oral cancer risk among Bangladeshi adults. Women [OR: 14.33 (95%CI: 6.33-32.42)] had the higher risk of developing oral cancer than men [OR: 5.29 (95%CI: 2.62-10.67)] from SLT use. Among men highest risk was observed among dual users (SLT and smoking) [OR: 17.23 (95%CI: 5.70-52.01)]. Both Betel Quid (BQ) with and without tobacco increased the oral cancer risk. However, the risk was lower for chewing BQ without tobacco than BQ with tobacco. The risk of oral cancer increased with the increasing frequency and intensity of SLT use. About 61% of all oral cancer cases in Bangladesh were attributable to SLT use. Among other oral cancer risk factors - bidi smoking, oral hygiene factors and leanness were associated with increased oral cancer risk. Conclusion: The findings of the present cross-sectional survey and hospital-based case-control study were comparable to existing literatures. Our evidence suggests that SLT use among rural Bangladeshi adolescent is low compared to other neighbouring countries. However, initiation of SLT at an early age is a public health concern. Lack of professional help to quit SLT and poor implementation of tobacco control laws were prevalent. Overall knowledge about SLT use and its ill effects was good, but misconceptions were prevalent. The case-control study demonstrated a significant increase of risk of oral cancer is associated with SLT use. Women had higher risk of developing oral cancer of SLT use than men. For men dual use of SLT and smoking was the major risk factor. Both BQ with and without tobacco was associated with oral cancer incidence. A large number of oral cancer cases in Bangladesh is preventable by tackling the SLT epidemic