Esophageal cancer in relation to alcohol drinking and tobacco use among men in Kerala, India – Karunagappally cohort

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Background

Tobacco use and alcohol consumption are considered the important risk factors for several types of cancers including esophageal cancer. Tobacco is used in different forms all around the world. The most common form of tobacco use worldwide is cigarette smoking. In Kerala, India, the most popularly smoked tobacco is bidi [ 1 ] among men, and tobacco chewing [ 2 ] is another common tobacco-related habit in men.

Cigarette smoking is an established risk factor for esophageal cancer [ 3 ]. Regarding bidi smoking, the available evidence is limited, as the habit is regionally specific; yet bidi smoking is a strong risk factor for the oral, lung, larynx, hypopharynx, and gastric cancers, and their associations were at least as strong as cigarette smoking [ 345 ]. A recent cohort study of 87,222 men in Mumbai, India, reported a significant association of bidi and/or cigarette smoking with an increased esophageal cancer incidence: hazard ratios [95 % confidence intervals (CIs)] were 5.46 (2.23–13.58) and 5.72 (2.38–13.58) and 5.72 (2.38–13.76) for bidi and cigarette smoking, respectively [ 6 ]. Previous case-control studies conducted in different parts of South India including Kerala showed that bidi smoking increased the risk of esophageal cancer several folds [ 789 ]. A case-control study which was carried out among males in Trivandrum, Kerala showed a significant association of bidi smoking with a higher risk of esophageal cancer (P < 0.001) [ 7 ]. A case-control study in Bangalore reported an odds ratio (OR) of 3.5 (95 % CI = 2.1–5.6) of bidi smoking [ 8 ]. Another case-control study from Chennai and Trivandrum reports that tobacco smoking was the strongest risk factor of esophageal cancer, OR = 2.83 (95 % CI = 2.18–3.66), however, this study did not take into account the types of smoking [ 10 ]. The epithelial cells lining the esophagus will have an inflammation when being exposed directly to carcinogens such as tobacco smoke and alcohol. Hazardous carcinogens in tobacco smoke may easily penetrate the esophageal epithelium and result in specific gene mutations. Esophageal cancer was considered to be causally related to tobacco smoking since 1986, and later IARC grouped tobacco as Group 1 carcinogen [ 3 ]. Alcohol can induce cellular damage and acetaldehyde; a reactive metabolite of ethanol is classified as a Group 1 carcinogen. Evidence supporting the association between alcohol consumption and increase in esophageal cancer risk has been considered sufficient since the publication of the 1988 IARC monograph [ 10 ] and the association has been confirmed by several studies globally thereafter, with a wide range of relative risks (RRs) obtained from studies in different geographical regions [ 11 ]. However, evidence investigating this association taking into account more detailed information of liquor and tobacco is scarce in India.

To date, the risk factors for esophageal cancer in India have been evaluated mainly by case-control studies [ 789 , 12 ]. The present study analyzed the risk of esophageal cancer in relation to tobacco use, alcohol drinking, and socio-economic status (SES) based on a cohort study in the rural population of Karunagappally, Kerala.