Contact with animals and risk of oesophageal squamous cell carcinoma: Outcome of a case-control study from Kashmir, a high-risk region

Background Several studies have reported association between animal contact and some cancer types, including lymphohaematopoietic, colon, pancreatic and neurological malignancies. We aimed to investigate the association between animal contact and risk of oesophageal squamous cell carcinoma (ESCC) in a case- control study in Kashmir, India, area with a relatively high incidence of ESCC. Methods We recruited 703 histologically confirmed ESCC cases and 1664 controls individually matched to the cases for age, sex and district of residence. Information, including on animal contact, was obtained in face-to-face interviews using a structured questionnaire. Conditional logistic regression models were used to calculate ORs and 95% CIs. Results As compared with no contact with animals, daily close contact was associated with an increased risk of ESCC (OR 5.99; 95% CI 3.86 to 9.31) in models adjusted for several potential confounding factors, including multiple indicators of socioeconomic status. This association persisted in subgroups following stratification by a composite wealth score and occupation. Irregular contact with animals was not associated with ESCC risk. The association between duration of animal contact and ESCC risk was mixed; however, contact for more than 50 years was associated with an increased risk (OR 3.10; 95% CI 1.53 to 6.26). Frequency (p for trend, 0.001) and duration (p for trend, <0.001) of animal contact showed dose-response association with ESCC risk. Conclusions Our results suggest an association between long-term and daily close contact with animals and ESCC. This association needs to be investigated in further studies.