Alcohol consumption plays a major role in India’s mouth cancer burden

Even a low daily intake of alcohol--just 9 g or around one standard drink-is linked to a 50% heightened risk of mouth (buccal mucosa) cancer in India, with the greatest risk associated with locally brewed alcohol, finds a large comparative study, published online in the open access journal BMJ Global Health.

And when combined with chewing tobacco, it likely accounts for 62% of all such cases in India, the findings suggest.

Mouth cancer is the second most common malignancy in India, with an estimated 143,759 new cases and 79,979 deaths every year. Rates of the disease have risen steadily, and now stand at just under 15 for every 100,000 Indian men, note the researchers.

The primary form of mouth cancer in India is that of the soft pink lining of the cheeks and lips (buccal mucosa). Less than half (43%) of those affected survive 5 or more years, they point out.

As alcohol consumption and tobacco use often go hand in hand, it's not clear how much each factor individually contributes to mouth cancer risk, especially in India, where the prevalence of smokeless tobacco use is high, point out the researchers. Nor have the potential effects of locally brewed alcohol, which is particularly popular in rural communities, been assessed, they add.

To find out more, the researchers compared 1803 people with confirmed buccal mucosa cancer and 1903 randomly selected people free of the disease (controls) from five different study centres between 2010 and 2021. Most of the participants were aged between 35 and 54; nearly half (around 46%) of cases were among 25 to 45 year olds.

Each of the participants provided information on the duration, frequency, and type of alcohol they drank from among 11 internationally recognised drinks, including beer, whisky, vodka, rum and breezers (flavoured alcoholic drinks); and 30 locally brewed drinks, including apong, bangla, chulli, desi daru, and mahua.

Participants were also asked about the duration and type of tobacco use so that the extent of the interaction between alcohol and tobacco on mouth cancer risk could be assessed.

Among the cases, 1019 said they didn't drink alcohol compared with 1420 among the controls; 781 of the cases said they did drink alcohol compared with 481 of the controls.

The average length of tobacco use was higher for cases (around 21 years) than for the control group (around 18 years). Cases were also more likely to live in rural areas and to drink more alcohol every day: nearly 37 g compared with around 29 g.

Frequent alcohol consumption was associated with a heightened risk of buccal mucosa cancer, with locally brewed drinks associated with the greatest risk.

Compared with those who didn't drink alcohol, the risk was 68% higher for those who did, rising to 72% for those favouring internationally recognised alcohol types, and to 87% for those opting for locally brewed drinks.

As little as under 2 g a day of beer was associated with a heightened risk of buccal mucosa cancer. And just 9 g a day of alcohol-equivalent to around one standard drink--was associated with an approximately 50% increased risk.

Concurrent alcohol and tobacco use was associated with a more than quadrupling in risk, such that 62% of all buccal mucosa cancer cases in India are likely attributable to the interaction between alcohol and chewing tobacco, calculate the researchers.

But alcohol was a contributory factor to the heightened risk of mouth cancer irrespective of how long tobacco had been used. Ethanol might alter the fat content of the inner lining of the mouth, increasing its permeability and therefore its susceptibility to other potential carcinogens in chewing tobacco products, explain the researchers.

The findings suggest that more than 1 in 10 cases (nearly 11.5%) of all buccal mucosa cancers in India are attributable to alcohol, rising to 14% in some of the states with a high prevalence of the disease, such as Meghalaya, Assam, and Madhya Pradesh, say the researchers. 

Possible contamination with toxins, such as methanol and acetaldehyde, in locally brewed alcohol, might help explain the higher risk associated with these drinks, the manufacture of which is largely unregulated, they suggest.

"The current legal framework for alcohol control in India is complex and involves both central and state laws. Central legislation provides protection of citizens where alcohol is included in the State List under the Seventh Schedule of the Indian Constitution, giving states the power to regulate and control alcohol production, distribution and sale. However, the locally-brewed liquor market is unregulated, with some forms used by participants containing up to 90% alcohol content," they point out.

They conclude: "In summary, our study demonstrates that there is no safe limit of alcohol consumption for [buccal mucosa cancer] risk…Our findings suggest that public health action towards prevention of alcohol and tobacco use could largely eliminate [buccal mucosa cancer] from India."