Dietary melatonin and liver cancer incidence in Japan: From the Takayama study.

There is some biological plausibility that exogenous melatonin plays a role in preventing liver carcinogenesis. There has been little research on the association between melatonin intake in a normal diet and health outcomes. We evaluated the association between dietary melatonin intake and the incidence of liver cancer in a population-based prospective study in Japan. This study included 30,824 residents of Takayama city who were 35 years of age or older in 1992 and had participated in the Takayama study, Japan. Dietary intake was assessed using a validated food frequency questionnaire at the baseline. Melatonin content in foods was measured by liquid chromatography-tandem mass spectrometry. Cancer incidence was confirmed through regional population-based cancer registries in Gifu. Liver cancer was defined as code C22 according to the International Classification of Diseases and Related Health Problems, 10th Revision. Hazard ratios for liver cancer were estimated for the tertile groups of melatonin intake using a Cox proportional hazards model. During the mean follow-up period of 13.6 years, 189 individuals developed liver cancer. Compared with subjects in the lowest tertile of melatonin intake, those in the middle and highest tertiles had decreased risks of liver cancer, with a significant linear trend after multivariate adjustments (hazard ratios: 0.64 and 0.65, respectively, trend p = 0.023). There was no significant interaction by sex (interaction p = 0.54). This initial finding, which needs to be confirmed by further studies, suggests that consuming melatonin-containing foods might play a role in the prevention of liver cancer.

Concerns about vaccines and vaccination behavior among Japanese budget travelers to India.

BACKGROUND: Low vaccination coverage among travelers poses a critical challenge to global health security. Indeed, public concerns regarding vaccines can lead to vaccine reluctance and refusal, but evidence about the impacts of concerns regarding vaccines on the uptake of travel vaccinations remains sparse. We examined the associations between concerns about vaccines and vaccination behavior among travelers. METHODS: Japanese travelers aged 18 years or older, who stayed at a guesthouse in New Delhi, India, were targeted (n = 153). We conducted cross-sectional surveys from August 23 to September 2, 2019, and from February 19 to March 5, 2020. We examined the associations of three concerns regarding vaccines (5-point scale)-serious side effects from vaccines, vaccine safety, and vaccine effectiveness-with the uptake of travel vaccinations. RESULTS: In total, 60 participants (39.2 %) had been vaccinated for this or a past trip. After adjusting for all potential confounding variables, concerns about serious side effects from vaccines and vaccine safety were negatively associated with the uptake of travel vaccinations. The ORs (95 % CIs) for 1-point increases in concerns about serious side effects from vaccines and vaccine safety were 0.72 (0.52, 0.99) and 0.71 (0.52, 0.96), respectively. Sensitivity analyses did not change the results substantially. CONCLUSIONS: Concerns about vaccine safety issues were negatively associated with the uptake of travel vaccinations among the participants, with no corresponding association observed for vaccine effectiveness. Addressing concerns about vaccine safety issues, rather than vaccine effectiveness may contribute to an increased uptake of travel vaccinations.