Tobacco, alcohol and dietary factors associated with the risk of oral cancer among Japanese.

The mortality rate among Japanese men due to oral cancer is increasing, but risk factors among Japanese other than smoking and drinking have not been examined. To investigate the dietary factors involved in oral cancer, we conducted a hospital-based case-referent study in Aichi, Japan. Cases comprised 189 men and 77 women aged 20-79 years with one of the following cancers: tongue, mouth, oropharynx and hypopharynx. The reference group comprised 9,858 male and 26,669 female out-patients without cancer. Smoking and drinking were highly associated with an increased risk of oral cancer. Japanese sake showed a lower odds ratio (OR) than beer or hard liquor (OR= 3.6, 4.5 and 4.8, respectively). In the cross analysis between smoking and drinking, smoking combined with drinking increased the risk of oral cancer to three times that of smoking only (OR=6.2 vs. 2.2). Frequent intake of raw vegetables (OR = 0.5) and fruit (OR = 0.5) were inversely associated with the risk of oral cancer after adjustment for age, sex, smoking, drinking and year of visit. Western-style breakfast and salty food preference decreased the risk of oral cancer, and salty food preference was still statistically significant by multivariate analysis (OR= 0.7). In conclusion, smoking cessation, drinking control and frequent intake of raw vegetables and fruit among Japanese are likely to be effective preventive measures against oral cancer.