SummaryBackground

Chewing tobacco and other types of smokeless tobacco use have had less attention from the global health community than smoked tobacco use. However, the practice is popular in many parts of the world and has been linked to several adverse health outcomes. Understanding trends in prevalence with age, over time, and by location and sex is important for policy setting and in relation to monitoring and assessing commitment to the WHO Framework Convention on Tobacco Control.

Methods

We estimated prevalence of chewing tobacco use as part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2019 using a modelling strategy that used information on multiple types of smokeless tobacco products. We generated a time series of prevalence of chewing tobacco use among individuals aged 15 years and older from 1990 to 2019 in 204 countries and territories, including age-sex specific estimates. We also compared these trends to those of smoked tobacco over the same time period.

Findings

In 2019, 273·9 million (95% uncertainty interval 258·5 to 290·9) people aged 15 years and older used chewing tobacco, and the global age-standardised prevalence of chewing tobacco use was 4·72% (4·46 to 5·01). 228·2 million (213·6 to 244·7; 83·29% [82·15 to 84·42]) chewing tobacco users lived in the south Asia region. Prevalence among young people aged 15–19 years was over 10% in seven locations in 2019. Although global age-standardised prevalence of smoking tobacco use decreased significantly between 1990 and 2019 (annualised rate of change: –1·21% [–1·26 to –1·16]), similar progress was not observed for chewing tobacco (0·46% [0·13 to 0·79]). Among the 12 highest prevalence countries (Bangladesh, Bhutan, Cambodia, India, Madagascar, Marshall Islands, Myanmar, Nepal, Pakistan, Palau, Sri Lanka, and Yemen), only Yemen had a significant decrease in the prevalence of chewing tobacco use, which was among males between 1990 and 2019 (−0·94% [–1·72 to –0·14]), compared with nine of 12 countries that had significant decreases in the prevalence of smoking tobacco. Among females, none of these 12 countries had significant decreases in prevalence of chewing tobacco use, whereas seven of 12 countries had a significant decrease in the prevalence of tobacco smoking use for the period.

Interpretation

Chewing tobacco remains a substantial public health problem in several regions of the world, and predominantly in south Asia. We found little change in the prevalence of chewing tobacco use between 1990 and 2019, and that control efforts have had much larger effects on the prevalence of smoking tobacco use than on chewing tobacco use in some countries. Mitigating the health effects of chewing tobacco requires stronger regulations and policies that specifically target use of chewing tobacco, especially in countries with high prevalence.

Funding

Bloomberg Philanthropies and the Bill & Melinda Gates Foundation.

IntroductionEffective design of tobacco-control policies and appropriate allocation of resources requires understanding patterns and trends in all types of tobacco use.1Giovino GA Biener L Hartman AM et al.Monitoring the tobacco use epidemic I. Overview: optimizing measurement to facilitate change. Although 138 (77%) of the 180 countries committed to the aims of the WHO Framework Convention on Tobacco Control (FCTC) include smokeless tobacco in their statutes,2Mehrotra R Yadav A Sinha DN et al.Smokeless tobacco control in 180 countries across the globe: call to action for full implementation of WHO FCTC measures. smokeless tobacco use has been monitored in far fewer countries than has smoking tobacco use, even in places with high prevalences of smokeless tobacco use.2Mehrotra R Yadav A Sinha DN et al.Smokeless tobacco control in 180 countries across the globe: call to action for full implementation of WHO FCTC measures. Only 55 (31%) FCTC countries have data on adult smokeless tobacco use from the past 10 years, and only 70 (39%) have data on smokeless tobacco use among young people.2Mehrotra R Yadav A Sinha DN et al.Smokeless tobacco control in 180 countries across the globe: call to action for full implementation of WHO FCTC measures. Additionally, smoked and smokeless tobacco use patterns differ by demographic, socioeconomic, and cultural characteristics,3Palipudi K Rizwan SA Sinha DN et al.Prevalence and sociodemographic determinants of tobacco use in four countries of the World Health Organization: South-East Asia region: findings from the Global Adult Tobacco Survey., 4Sinha DN Rizwan SA Aryal KK Karki KB Zaman MM Gupta PC Trends of smokeless tobacco use among adults (aged 15–49 years) in Bangladesh, India and Nepal., 5Sinha DN Kumar A Bhartiya D et al.Smokeless tobacco use among adolescents in global perspective., 6Kakde S Bhopal RS Jones CM A systematic review on the social context of smokeless tobacco use in the South Asian population: implications for public health. so detailed information on smokeless tobacco use patterns and trends are needed to tailor interventions that best meet the needs of these different subgroups.Monitoring of smokeless tobacco use alongside smoked tobacco use should be done for a variety of reasons, including beliefs that it is a safe alternative to smoking, beliefs about a variety of benefits (eg, for morning sickness), and local distribution and production.6Kakde S Bhopal RS Jones CM A systematic review on the social context of smokeless tobacco use in the South Asian population: implications for public health., 7Factors contributing to nass consumption among Iranian Turkmen: a qualitative study., 8Kumar G Pednekar MS Narake S Dhumal G Gupta PC Feedback from vendors on gutka ban in two states of India. Moreover, smokeless tobacco is less regulated than smoked tobacco. Tobacco manufacturers can sell smokeless tobacco products that are sweeter or flavoured and aimed at new users,9Tobacco industry use of flavourings to promote smokeless tobacco products. and these products are usually cheaper than cigarettes.10Determinants of smokeless tobacco use in India. A wide array of products is available in the market, but data on smokeless tobacco use are often not collected by specific products or subtypes, further complicating monitoring and regulation. Although all smokeless tobacco products are consumed through the mouth or nose without burning, the wide variety of products are used in different ways11Siddiqi K Husain S Vidyasagaran A Readshaw A Mishu MP Sheikh A Global burden of disease due to smokeless tobacco consumption in adults: an updated analysis of data from 127 countries. and are associated with varying degrees and types of harm.12Boffetta P Aagnes B Weiderpass E Andersen A Smokeless tobacco use and risk of cancer of the pancreas and other organs., 13Stepanov I Yershova K Carmella S Upadhyaya P Hecht SS Levels of (S)-N'-nitrosonornicotine in U.S. tobacco products., 14Asthana S Labani S Kailash U Sinha DN Mehrotra R Association of smokeless tobacco use and oral cancer: a systematic global review and meta-analysis. This study focuses on chewing tobacco use, because the associated health risks are well documented.12Boffetta P Aagnes B Weiderpass E Andersen A Smokeless tobacco use and risk of cancer of the pancreas and other organs., 15Sinha DN Suliankatchi RA Gupta PC et al.Global burden of all-cause and cause-specific mortality due to smokeless tobacco use: systematic review and meta-analysis., 16Teo KK Ounpuu S Hawken S et al.Tobacco use and risk of myocardial infarction in 52 countries in the INTERHEART study: a case-control study. Many studies have found strong evidence for the increased risk of oral cancer due to chewing tobacco.11Siddiqi K Husain S Vidyasagaran A Readshaw A Mishu MP Sheikh A Global burden of disease due to smokeless tobacco consumption in adults: an updated analysis of data from 127 countries., 14Asthana S Labani S Kailash U Sinha DN Mehrotra R Association of smokeless tobacco use and oral cancer: a systematic global review and meta-analysis., 17Systematic review and meta-analysis of association of smokeless tobacco and of betel quid without tobacco with incidence of oral cancer in South Asia and the Pacific.Research in context

Evidence before this study

Previous studies of smokeless tobacco use have found that both prevalence and the type of product used vary widely across countries. Studies on the health effects of smokeless tobacco products have found differences in toxicity by type of product, with chewing tobacco products being the most harmful. Limitations of available survey data have posed a challenge to estimating internally consistent and comparable estimates of product-specific prevalence, disaggregated by location, age, sex, and time period. These limitations have made it difficult to form a comprehensive, global picture of where chewing tobacco is used most, among which age groups and sexes, and how this has changed over time.

Added value of this study

This study, based on results from the Global Burden of Diseases, Injuries, and Risk Factors Study 2019, is the first global analysis of prevalence of chewing tobacco use by age, sex, and time period that incorporates information from available nationally representative surveys with questions about smokeless tobacco use. To address the challenge of heterogeneous survey data, of which little were available, we developed and implemented a new approach to combining different definitions and sources of smokeless tobacco prevalence data across locations to mitigate the effects of compositional bias in the available data. These methods improved estimates, particularly in locations that have less chewing tobacco-specific data but do have data on other smokeless tobacco products. This modelling approach allowed for the use 752 data sources, integral to producing improved estimates by age, sex, and location, across which prevalence of chewing tobacco use varies widely. Finally, we compared trends in chewing tobacco with trends in smoking prevalence. The difference in trends over time between prevalences of chewing and smoking tobacco indicates that tobacco control efforts and policies have had a much larger effect on the prevalence of smoking tobacco use than on the prevalence of chewing tobacco use.

Implications of all the available evidence

Monitoring of prevalence of chewing tobacco use would benefit greatly from concerted efforts to add questions about its use in surveys that clearly distinguish the types of products, in a similar way to what is done for smoking tobacco. We found that the prevalence of chewing tobacco use has remained fairly stable over time and is high in many regions and demographic groups, including those with historically lower prevalence of smoking tobacco. Increased commitment to control of smokeless tobacco through both local interventions and expansion of the policies outlined in the WHO Framework Convention on Tobacco Control articles to smokeless tobacco products is urgently needed.

In this context, we aimed to provide an improved understanding of chewing tobacco use, which is essential for targeted policy, assessment of the effectiveness of these policies, and, ultimately, mitigation of the associated harms.1Giovino GA Biener L Hartman AM et al.Monitoring the tobacco use epidemic I. Overview: optimizing measurement to facilitate change. Studies have been done previously that estimated prevalence for a particular country,18Patterns of tobacco use across rural, urban, and urban-slum populations in a north Indian community., 19Krishnamoorthy Y Ganesh K Spatial pattern and determinants of tobacco use among females in India: evidence from a nationally representative survey., 20Al-Tayar B Tin-Oo MM Sinor MZ Alakhali MS Prevalence and association of smokeless tobacco use with the development of periodontal pocket among adult males in Dawan Valley, Yemen: a cross-sectional study. region,3Palipudi K Rizwan SA Sinha DN et al.Prevalence and sociodemographic determinants of tobacco use in four countries of the World Health Organization: South-East Asia region: findings from the Global Adult Tobacco Survey., 4Sinha DN Rizwan SA Aryal KK Karki KB Zaman MM Gupta PC Trends of smokeless tobacco use among adults (aged 15–49 years) in Bangladesh, India and Nepal., 21Sreeramareddy CT Pradhan PM Sin S Prevalence, distribution, and social determinants of tobacco use in 30 sub-Saharan African countries. or source,3Palipudi K Rizwan SA Sinha DN et al.Prevalence and sociodemographic determinants of tobacco use in four countries of the World Health Organization: South-East Asia region: findings from the Global Adult Tobacco Survey., 18Patterns of tobacco use across rural, urban, and urban-slum populations in a north Indian community., 19Krishnamoorthy Y Ganesh K Spatial pattern and determinants of tobacco use among females in India: evidence from a nationally representative survey., 20Al-Tayar B Tin-Oo MM Sinor MZ Alakhali MS Prevalence and association of smokeless tobacco use with the development of periodontal pocket among adult males in Dawan Valley, Yemen: a cross-sectional study., 21Sreeramareddy CT Pradhan PM Sin S Prevalence, distribution, and social determinants of tobacco use in 30 sub-Saharan African countries. or a restricted time period11Siddiqi K Husain S Vidyasagaran A Readshaw A Mishu MP Sheikh A Global burden of disease due to smokeless tobacco consumption in adults: an updated analysis of data from 127 countries., 20Al-Tayar B Tin-Oo MM Sinor MZ Alakhali MS Prevalence and association of smokeless tobacco use with the development of periodontal pocket among adult males in Dawan Valley, Yemen: a cross-sectional study., 21Sreeramareddy CT Pradhan PM Sin S Prevalence, distribution, and social determinants of tobacco use in 30 sub-Saharan African countries. or age group,5Sinha DN Kumar A Bhartiya D et al.Smokeless tobacco use among adolescents in global perspective., 22Choi S Kim Y Lee J Kashiwabara M Oh K Tobacco use among students aged 13–15 years in South Korea: the 2013 Global Youth Tobacco Survey. but to our knowledge no attempt has been made to synthesise multiple data sources to understand these trends globally over time and across age groups. For the first time, as part of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019, we comprehensively estimated the prevalence of chewing tobacco use using all available data sources to estimate age-sex-specific prevalence of chewing tobacco use from 1990 to 2019 in 204 countries and territories. We also compared these trends with those of smoked tobacco over the same time period.23GBD 2019 Tobacco Collaborators
Spatial, temporal, and demographic patterns in prevalence of smoking tobacco use and attributable disease burden in 204 countries and territories, 1990–2019: a systematic analysis from the Global Burden of Disease Study 2019. This manuscript was produced as part of the GBD Collaborator Network and in accordance with the GBD Protocol.Methods Overview and definitionsWe modelled prevalence of current chewing tobacco use by using data on multiple types of smokeless tobacco use. We defined current chewing tobacco use as use of chewing tobacco products within the past 30 days on either a daily or occasional basis, or current use as defined by the survey. We produced estimates for males and females separately, and for each 5-year age group between the ages of 15 and 94 years with a terminal age group of individuals aged 95 years and older. We produced estimates for every year between 1990 and 2019 and for 204 countries and territories included in GBD 2019. This study adheres to the Guidelines for Accurate and Transparent Health Estimates Reporting.24Stevens GA Alkema L Black RE et al.Guidelines for Accurate and Transparent Health Estimates Reporting: the GATHER statement.

Because data on chewing tobacco alone are sparse, we systematically reviewed, extracted, and included in our estimations data on all types of smokeless tobacco. We classified data into three categories: chewing tobacco products only, non-chewing tobacco products only, and general smokeless tobacco with products not specified; we refer to this third category as unspecified smokeless tobacco. The first and second categories are distinct and do not overlap. Available data in these two categories were used to adjust data reported as general smokeless tobacco, which comprises the majority of data sources. As a result, in our modelling process we used information from all three categories to produce our final estimates of prevalence of chewing tobacco use for all countries.

 Data sourcesWe searched the Global Health Data Exchange for representative surveys with data on use of any smokeless tobacco product among individuals aged 10 years and older collected between 1980 and 2019. Although we report data for individuals aged 15 years and older and from 1990 onwards, we included this additional age group and decade to inform time trends and age patterns of the model. We included individual-level survey data, tabulated survey report data, and data from scientific literature. We identified and extracted data from 752 surveys that were location and year specific that met our inclusion criteria. Of 204 countries and territories, 185 (91%) had at least one data source and 58 (28%) had at least five data sources. 57 countries (28%) had their most recent data source from either 2017 or 2018. Full details on inclusion criteria, search strings, and extraction methods are included in the appendix (pp 12–15). A list of all included surveys can be accessed through the GBD 2019 Data Input Sources Tool. Modelling strategy and overview of spatiotemporal Gaussian process regressionA key challenge in modelling the prevalence of chewing tobacco use is that 562 (75%) of 752 sources with information on smokeless tobacco did not distinguish between specific smokeless tobacco products. Because this large proportion of sources reported on unspecified smokeless tobacco use, we used a modelling strategy that maximised the use of available information, rather than constraining our analysis to only focus on sources reporting the prevalence of chewing tobacco use alone. An overview of the modelling strategy, from data processing to final prevalence estimates, is shown in the appendix (p 23).In three different parts of the estimation process, we used spatiotemporal Gaussian process regression (ST-GPR) to model location-age-sex-specific trends over time. Details on ST-GPR are described in full elsewhere.25GBD 2019 Risk Factor Collaborators
Global burden of 87 risk factors in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019. Briefly, the model is implemented in three steps: first, linear regression; second, spatiotemporal smoothing, which adjusts the linear regression estimate on the basis of residuals weighted by distance in time, age, and location; and finally, Gaussian process regression, which incorporates uncertainty in the data and quantifies the uncertainty of the estimates. For all ST-GPR models, we used an agnostic first-stage linear model that only includes a global intercept and age fixed effects. As a result, variations in final estimates by time, location, and age were entirely data driven and were incorporated in the second and third stages of the model. The information sharing across similar locations in ST-GPR is particularly useful in this context because the proportion of chewing tobacco use versus non-chewing tobacco use appears to be very similar within geographical regions.11Siddiqi K Husain S Vidyasagaran A Readshaw A Mishu MP Sheikh A Global burden of disease due to smokeless tobacco consumption in adults: an updated analysis of data from 127 countries. Additionally, we do not believe that these trends over age and time are substantially affected by different survey methods (appendix p 20). The end result of ST-GPR is 1000 draws from the posterior distribution of the Gaussian process, from which we calculated the mean and 2·5th and 97·5th percentiles to characterise the 95% uncertainty interval (UI). Smokeless tobacco product mapping and generation of the prevalence modelCase definitions varied substantially across data sources. Surveys reported on 262 unique combinations of smokeless tobacco products, which we mapped to one of two mutually exclusive and collectively exhaustive categories: either chewing tobacco products or non-chewing tobacco products. Non-chewing tobacco products refers to smokeless tobacco products that are not chewing tobacco. In some cases, surveys did not specify a product, or specified a wide array of products that spanned both categories. We mapped these sources to a third category of unspecified smokeless tobacco. The product map is in the appendix (p 15). After product mapping, 170 sources reported on the prevalence of chewing tobacco use, 137 reported on the prevalence of non-chewing tobacco use, and 690 reported on the prevalence of unspecified smokeless tobacco use.After product mapping, 141 (19%) of 752 sources reported data only in aggregated age groups or as both sexes combined. We split these data into our standard 5-year age groups by sex. To do so, we ran separate ST-GPR models for each of the product categories (chewing tobacco, non-chewing tobacco, and unspecified smokeless tobacco), using only data originally available in our standard 5-year age groups and separately by sex. In these models, we purposefully tuned the parameter controlling the decay function for age weights in the spatiotemporal smoothing step to ensure that age patterns were data driven rather than model driven. We then used the modelled estimates to generate age and sex ratios that included uncertainty and varied by location and year. We applied these ratios to the data originally reported in aggregated age groups or as both sexes combined to split the aggregated data into our target demographic groups. Additional details on these methods are in the appendix (pp 16–17).The proportion of unspecified smokeless tobacco that is chewing tobacco varies widely across countries. For example, in Sweden, snus (pulverised tobacco for sublabial administration, which we classify as non-chewing tobacco)26Leon ME Lugo A Boffetta P et al.Smokeless tobacco use in Sweden and other 17 European countries. is the predominant product used, while in India, most users of smokeless tobacco use chewing tobacco.6Kakde S Bhopal RS Jones CM A systematic review on the social context of smokeless tobacco use in the South Asian population: implications for public health. To include data sources that report the prevalence of unspecified smokeless tobacco use, we needed an estimate of the proportion of unspecified smokeless tobacco that is chewing tobacco in each country.

To arrive at that proportion, first we ran separate models for chewing tobacco and non-chewing tobacco, using all available data for each indicator. Then, based on the results of these models, we estimated an age-sex-location-year-specific ratio of chewing tobacco as a proportion of chewing and non-chewing tobacco. Finally, we used this estimated ratio to adjust data reported as prevalence of unspecified smokeless tobacco use. We added the variance of the estimated ratio to the original variance of the data to reflect the uncertainty in this adjustment.

The final step in our modelling process was a ST-GPR model that included all data reported as prevalence of chewing tobacco use, and data reported as unspecified smokeless tobacco that have been adjusted on the basis of the estimated product type ratio. Because data variance is an input to ST-GPR, datapoints with higher variance had a lower influence on final estimates than did datapoints with a lower variance. As a result, the adjusted datapoints added information to the final model, but were weighted less in the final estimation than datapoints that were reported directly as prevalence of chewing tobacco use. Additional details of these methods are in the appendix (pp 18–20). Statistical analysis

We report the prevalence of chewing tobacco use and the number of people that currently use chewing tobacco, by location, year, age, and sex, as well as age-standardised estimates for individuals aged 15 years and older, all with their respective 95% UIs. Similarly we report prevalences by sex among individuals aged 15–19 years. We calculated annualised rates of change to assess time trends and compare changes across time with those observed for the prevalence of smoking tobacco use. We calculated all results (including annualised rates of change) that are reported as geographical aggregations using population-weighted aggregation. We determined annualised rates of change to be significant if the 95% UI did not include zero. We considered prevalence results to be significantly different if their 95% UIs did not intersect.

Details on modelling the prevalence of smoking tobacco use have been published separately.23GBD 2019 Tobacco Collaborators
Spatial, temporal, and demographic patterns in prevalence of smoking tobacco use and attributable disease burden in 204 countries and territories, 1990–2019: a systematic analysis from the Global Burden of Disease Study 2019. Additionally, we did a sensitivity analysis comparing the results of this main method (using both chewing tobacco and adjusted unspecified smokeless tobacco data) versus the results of using only the data on chewing tobacco (appendix pp 28–29).

We did all analyses using R (version 3.6.3).

 Role of the funding source

The funders of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report.

ResultsGlobally, 273·9 million (95% UI 258·5–290·9) people used chewing tobacco in 2019 (appendix pp 62–69). The global age-standardised prevalence of chewing tobacco use in 2019 among people aged 15 years and older was 4·72% (4·46–5·01) and was 6·55% (6·10–7·03) among males and 2·87% (2·60–3·14) among females (table). Most people (228·2 million [213·6–244·7]; 83·29% [82·15–84·42]) who used chewing tobacco in 2019 resided in the south Asia region. The largest populations of people who use chewing tobacco are in India (185·8 million [171·3–202·5] users; 67·83% [65·77–69·75] of global users) and Bangladesh (25·7 million [23·7–27·6]; 9·37% [8·59–10·25] of global users. Nepal, Bhutan, and Palau also had very high prevalences of chewing tobacco use in 2019, with 4·4 million (4·1–4·8) users in Nepal, 113 040 (102 587–123 860) in Bhutan, and 3440 (3090–3819) in Palau. Among males aged 15 years and older in 2019, the age-standardised prevalence in south Asia was 24·65% (22·81–26·69), while the lowest prevalence globally was 0·17% (0·15–0·20) in southern Latin America (figure 1; appendix p 70). Similarly, the age-standardised prevalence for females in south Asia was 12·13% (10·91–13·45) in 2019, much greater than the lowest age-standardised prevalence globally, which was in western Europe (0·15% [0·14–0·17]; figure 1; appendix p 69). Outside of the south Asia region, the countries with the highest prevalence of chewing tobacco use in 2019 were, for males, Palau (25·76% [22·37–29·75]), Madagascar (16·98% [14·66–19·30]), Myanmar (14·18% [11·94–16·53]), and Sri Lanka (13·57% [11·39–15·77]; figure 1; appendix pp 30–37). For females, the highest prevalence of use was observed in Palau (24·42% [20·04–29·17]), Cambodia (12·84% [11·05–14·70]), Laos (6·73% [5·31–8·24]), and Botswana (6·54% [5·32–7·92]; figure 1; appendix pp 30–37).

Table