Study Finds Chewing Tobacco Raises Mouth Cancer Risk More Than Smoking

A recent study reveals that habitual chewing tobacco use increases the risk of mouth cancer more than smoking. This article examines study details, explains how chewing tobacco damages oral tissues, includes expert insights, and discusses public health implications and prevention strategies.

Oral cancer claims hundreds of thousands of lives each year, and while smoking has long been established as a primary risk factor, emerging evidence now shows that chewing tobacco poses an even greater threat to oral health. A recent cohort study in Kerala, India, followed more than 78,000 women over 15 years and found that those who chewed tobacco ten times or more a day had a 9.2-fold increase in oral cancer incidence compared to non-chewers. In contrast, smoking typically elevates oral cancer risk by five to ten times. This startling finding underscores the urgent need to reframe public health messaging and regulatory efforts around smokeless tobacco products.

Study Overview

Researchers from the Karunagappally Cancer Registry initiated a population-based cohort study between 1990 and 1997, enrolling 92 000 women aged 30 to 84 years and tracking cancer incidence until 2005. After excluding occasional smokers and alcohol consumers, 78 140 women remained in the analysis, among whom 92 developed histopathologically confirmed oral cavity cancers. Key features included:

• Sample size: 78 140 non-smoking, non-drinking women
• Duration: Average follow-up of 8 to 15 years
• Outcome measure: Relative risk (RR) of oral cavity cancer
• Analysis: Poisson regression adjusted for age and income

The study found a clear dose–response relationship. Women who chewed tobacco 1–9 times daily saw a moderate increase in risk, while those chewing ten times or more per day exhibited a 9.2-fold heightened risk. Moreover, the association strengthened with cumulative years of chewing during the first 20 years of use but plateaued thereafter.

Biological Mechanisms of Chewing Tobacco Carcinogenicity

Chewing tobacco introduces high concentrations of carcinogens particularly tobacco-specific nitrosamines (TSNAs) and polycyclic aromatic hydrocarbons directly to the oral mucosa. Frequent mechanical irritation from quid particles exacerbates mucosal damage, leading to:

• DNA adduct formation by TSNAs causing mutations in oncogenes and tumor suppressor genes
• Chronic inflammation and oxidative stress, which promote dysplasia
• Impaired DNA repair mechanisms in oral epithelial cells

In comparison, smoking delivers carcinogens primarily to the lungs and systemic circulation, with less direct contact time in the oral cavity. Although smoking still poses a significant risk estimated at a 5 to 10-fold increase for heavy smokers the combination of concentrated TSNAs, constant mucosal contact, and physical abrasion makes chewing tobacco particularly harmful to oral tissues.

Expert Insights

Oncologists and public health officials emphasize the gravity of these findings:

• “Smokeless tobacco products are often perceived as safer alternatives, yet they deliver potent carcinogens directly to oral tissues,” explains Dr. Richa Mehta, Head of Oncology at All India Institute of Medical Sciences. “This study highlights that habitual chewing tobacco can be more carcinogenic to the mouth than smoking”.
• Public health specialist Dr. Arvind Patel of the National Cancer Registry remarks, “Regulatory efforts have largely focused on cigarettes, but we must extend stringent controls including taxation and warning labels to all tobacco products to curb the rising oral cancer burden.”
• Maulana Azad Medical College’s Dr. Parth Sharma, lead author of a cross-sectional study in Delhi, notes, “Affordable chewing tobacco continues to fuel cancer cases in low-income urban populations. Without explicit warnings about oral cancer, many users remain unaware of the specific risks”.

Public Health Implications

In regions where chewing tobacco is ingrained in cultural practices such as India, South Asia, and parts of the United States oral cancer incidence remains disproportionately high. The Global Burden of Disease collaborates data indicating that smokeless tobacco contributes to approximately one-third of oral cancer cases worldwide.

Key challenges include:

• Widespread availability of gutka, kharra, and chewable quid despite bans
• Limited awareness of specific health hazards, with only 66 percent of Delhi study participants linking chewing tobacco to oral cancer
• Inadequate warning labels lacking clear imagery of mouth lesions
• Social acceptance and cultural norms that downplay the danger of chewing tobacco

Addressing these issues requires multifaceted strategies:

• Stricter enforcement of existing bans on manufacturing and sale
• Prominent, graphic warning labels depicting oral cancer lesions
• Targeted education campaigns in local languages, focusing on low-income and rural communities
• Integration of oral cancer screening into primary healthcare services

Conclusion

Chewing tobacco is far from a harmless habit it is a powerful cause of oral cancer, often more dangerous than smoking. The Kerala cohort study provides compelling evidence that frequent users face an exceptionally high risk, especially when chewing ten or more times a day. The combination of direct exposure to carcinogens, constant irritation of oral tissues, and long-term use creates the perfect conditions for cancer development.

These findings call for urgent public health action. Awareness campaigns must challenge the misconception that smokeless tobacco is a safer option. Regulations should tighten on production, sales, and advertising, ensuring that warning labels depict the real consequences of oral cancer. Integrating oral cancer screening into community health programs can help detect early signs, particularly in high-risk populations.

Ultimately, reducing oral cancer rates requires collective effort from individuals who choose to quit, to healthcare providers who promote cessation, to policymakers who enforce stronger controls. The message is simple but vital: no form of tobacco is safe. Ending both smoking and chewing habits is the only reliable way to protect oral health and save lives from one of the world’s most preventable cancers.

Source: Tobacco chewing and female oral cavity cancer risk in the Karunagappally cohort, India & A study finds it is fuelling cancer faster than cigarettes

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