Tooth brushing, tooth loss, and risk of upper aerodigestive tract cancer: a cohort study of Japanese dentisits.

Previous studies have focused on the association between poor oral health and upper aerodigestive tract (UADT) cancer. However, whether toothbrushing and tooth loss are associated with UADT cancer risk is still unclear. Therefore, we investigated the association between toothbrushing or tooth loss and UADT cancer in the Longitudinal Evaluation of Multi-phasic, Odontological, and Nutritional Associations in Dentists (LEMONADE) cohort study. From 2001 to 2006, we recruited 20,445 dentists (mean age ± standard deviation, 51.8 ± 12.0 years; 1,607 women [7.9%]) and followed for incidence or mortality of UADT cancer through March 2014. Information on lifestyle and oral health was collected by the baseline questionnaire. The Cox proportional hazards model was used to estimate hazard ratios (HRs) for UADT cancer and corresponding 95% confidence intervals (CI) for brushing frequency and tooth loss with adjustment for covariates. During the mean follow-up of 9.5 years, we confirmed 62 incident or fatal cases of UADT cancer. Infrequent toothbrushing (< 2 times/day) was significantly associated with increased risk of UADT cancer (multivariate HR = 2.13, 95% CI: 1.04-4.37). On the contrary, tooth loss was not significantly correlated with UADT cancer risk; multivariate HR was 1.03 (95% CI: 0.41-2.61) for loss of 15-27 teeth and 1.37 (0.50-3.75) for that of 28 teeth compared to tooth loss of 0-14 teeth. In conclusion, Infrequent toothbrushing was significantly associated with the risk of UADT cancer.