A novel environmental exposure index and its interaction with familial susceptibility on oral cancer in non-smokers and non-drinkers: a case-control study.

The objective of this study was to explore the collective effect of environmental factors and its interaction with familial susceptibility on oral cancer among non-smokers and non-drinkers (NSND). A hospital-based case-control study, including 319 oral cancer patients and 994 frequency-matched controls, was conducted in Fujian, China. We raised a weighed environmental exposure index according to nine significant environmental factors obtained from multivariable logistic regression model. And then, the index was classified into three categories according to the tertiles of controls (<1.34, 1.34-2.43, and >2.43). Multiplicative and additive interactions were evaluated between environmental exposure index and family cancer history. Our results showed that environmental exposure index was associated with an increased risk of oral cancer especially for those with family cancer history. Compared to subjects with low environmental exposure index and without family cancer history, those with high index and family cancer history showed the highest magnitude of OR in oral cancer risk (OR 10.40, 95% CI 5.46-19.80). Moreover, there was a multiplicative interaction between environmental exposure index and family cancer history for the risk of oral cancer (P < 0.001). This study puts forward a novel environmental exposure index, which enables a comprehensive evaluation on the overall effect of environmental risk factors on oral cancer among NSND and may interact with family cancer history. Further studies are warranted to explore the underlying mechanisms.