片桐 諒子

Given the female predominance of thyroid cancer (TC), particularly in the reproductive age range, female sex hormones have been proposed as an aetiology; however, previous epidemiological studies have shown conflicting results. We conducted a pooled analysis using individual data from 9 prospective cohorts in the Asia Cohort Consortium, to explore the association between 10 female reproductive and hormonal factors and TC risk. Using Cox proportional hazards models, cohort-specific hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated and then pooled using a random-effects model. Analyses were stratified by country, birth years, smoking status, body mass index, and TC risk based on age of diagnosis was also examined. Among 259,649 women followed for a mean 17.2 years, 1,353 incident TC cases were identified, 88% (n=1,140) being papillary TC. Older age at first delivery (≥26 vs 21-25 years) was associated with increased TC risk (p-trend=0.003, HR=1.16, 95% CI:1.03-1.31), particularly when diagnosed later in life (≥55 vs <55 years) [p-trend=0.003; HR=1.19, 95% CI:1.02-1.39]. Among younger birth cohorts, women with more number of deliveries showed an increased TC risk [p-trend=0.0001, HR=2.40, 95% CI:1.12-5.18 (≥5 vs 1-2 children)], and there was no substantial trend in older cohorts. Distinct patterns were observed for the number of deliveries and TC risk across countries, with a significant positive association for Korea [p-trend=0.0008, HR=1.89, 95% CI:1.21-2.94 (≥5 vs 1-2 children)], and non-significant inverse associations for China and Japan. Contextual and macrosocial changes in reproductive factors in Asian countries may influence thyroid cancer risk.

BACKGROUND: There are scarce data on risk factors for epithelial ovarian cancer (EOC) in Asian populations. Our goal was to advance knowledge on reproductive -related risk factors for EOC in a large population of Asian women. METHODS: This study used pooled individual data from baseline questionnaires in 11 prospective cohorts (baseline years, 1958-2015) in the Asia Cohort Consortium. A Cox proportional hazards regression model was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) adjusting for age, parity and cohort. RESULTS: After a mean = 17.0 years (SD = 6.3) of follow-up, 674 incident invasive EOC cases were identified among 325,626 women. In multivariable adjusted models we observed an inverse association with parity (5+ children vs. 0, HR = 0.44, 95% CI = 0.28-0.68, Ptrend < 0.001), and a positive association with increasing menopausal age (55+ years vs. <45, HR = 1.77, 95% CI = 1.05-3.01, Ptrend = 0.02) for risk of all EOC. CONCLUSIONS: In this large study of Asian women we identified an inverse association with parity and a positive association with higher menopausal age in relation to EOC risk. Further work is needed to understand EOC risk factors for rare histologic subtypes that occur more frequently in Asian populations.

Several epidemiological studies have investigated the circulating levels of albumin, bilirubin, and uric acid (UA) in relation to cancer risk; however, they have provided equivocal evidence. In this prospective case-cohort study, we aimed to explore the association of plasma albumin, bilirubin, and UA levels with cancer incidence. We measured the plasma levels of albumin, bilirubin, and UA and investigated their association with cancer incidence in 3,584 cases and 4,270 randomly selected participants with a median follow-up of 15.8 years. The adjusted hazard ratios (HR) and 95% confidence intervals (CI) of total cancer for the highest (Q4) versus lowest quartile (Q1) was 0.77 (95% CI: 0.67-0.90, P for trend: <0.001) for albumin. This association was attenuated after excluding liver cancer cases with lower plasma albumin levels. Plasma bilirubin levels were positively related to liver cancer but inversely to total cancer after excluding liver cancer with adjusted HR Q4 vs. Q1 of 0.86 (95% CI: 0.74-0.99, P for trend = 0.015). Plasma UA levels were not dose-responsively associated with total cancer risk. Higher plasma bilirubin levels were associated with a decreased risk of total cancer after excluding liver cancer, which is likely attributed to the antioxidant properties of bilirubin.

PURPOSE: Dietary fiber is a possible nutritional component which aids in the prevention of visceral fat accumulation. We examined the association between dietary fiber intake and visceral fat volume (VFV) by sex, and further analysed the association by major food sources of dietary fiber. METHODS: In this cross-sectional study, we measured VFV in 2779 Japanese (1564 men and 1215 women) aged 40-89 who underwent positron emission tomography/computed tomography for cancer screening between 2004 and 2005. Dietary fiber intake was calculated based on a validated semi-quantitative food frequency questionnaire. The association between dietary fiber intake and VFV was investigated using multivariate linear regression models after adjustment for potential confounders. RESULTS: Total, soluble, and insoluble fiber intakes were inversely associated with VFV in men (Q1: 3740 cm3, Q4: 3517 cm3, Ptrend: 0.0006 for total fiber), but not in women (Q1: 2207 cm3, Q4: 2193 cm3,Ptrend: 0.88 for total fiber). Statistically significant sex difference was observed (Pinteraction = 0.001 for total fiber). Subgroup analyses by major food sources revealed that dietary fiber intakes from beans, vegetables and fruits showed an inverse association with VFV in men, while cereal fiber intake showed a tendency toward a positive association in both sexes (Q1: 3520 cm3, Q4: 3671 cm3, Ptrend: 0.05 in men, Q1: 2147 cm3, Q4: 2227 cm3, Ptrend: 0.10 in women). CONCLUSION: We observed a sex-specific association between dietary fiber intake and VFV in Japanese adults. This study suggests that efforts against visceral fat accumulation should take account of the source of dietary fiber.