Vegetable intake and the risk of bladder cancer in the BLadder Cancer Epidemiology and Nutritional Determinants (BLEND) international study.

Although a potential inverse association between vegetable intake and bladder cancer risk has been reported, epidemiological evidence is inconsistent. This research aimed to elucidate the association between vegetable intake and bladder cancer risk by conducting a pooled analysis of data from prospective cohort studies.

Vegetable intake in relation to bladder cancer risk was examined by pooling individual-level data from 13 cohort studies, comprising 3203 cases among a total of 555,685 participants. Pooled multivariate hazard ratios (HRs), with corresponding 95% confidence intervals (CIs), were estimated using Cox proportional hazards regression models stratified by cohort for intakes of total vegetable, vegetable subtypes (i.e. non-starchy, starchy, green leafy and cruciferous vegetables) and individual vegetable types. In addition, a diet diversity score was used to assess the association of the varied types of vegetable intake on bladder cancer risk.

The association between vegetable intake and bladder cancer risk differed by sex (P-interaction = 0.011) and smoking status (P-interaction = 0.038); therefore, analyses were stratified by sex and smoking status. With adjustment of age, sex, smoking, energy intake, ethnicity and other potential dietary factors, we found that higher intake of total and non-starchy vegetables were inversely associated with the risk of bladder cancer among women (comparing the highest with lowest intake tertile: HR = 0.79, 95% CI = 0.64-0.98, P = 0.037 for trend, HR per 1 SD increment = 0.89, 95% CI = 0.81-0.99; HR = 0.78, 95% CI = 0.63-0.97, P = 0.034 for trend, HR per 1 SD increment = 0.88, 95% CI = 0.79-0.98, respectively). However, no evidence of association was observed among men, and the intake of vegetable was not found to be associated with bladder cancer when stratified by smoking status. Moreover, we found no evidence of association for diet diversity with bladder cancer risk.

Higher intakes of total and non-starchy vegetable are associated with reduced risk of bladder cancer for women. Further studies are needed to clarify whether these results reflect causal processes and potential underlying mechanisms.

BMC medicine. 2021 Mar 09*** epublish ***

Evan Yi-Wen Yu, Anke Wesselius, Siamak Mehrkanoon, Mieke Goosens, Maree Brinkman, Piet van den Brandt, Eric J Grant, Emily White, Elisabete Weiderpass, Florence Le Calvez-Kelm, Marc J Gunter, Inge Huybrechts, Elio Riboli, Anne Tjonneland, Giovanna Masala, Graham G Giles, Roger L Milne, Maurice P Zeegers

Department of Complex Genetics and Epidemiology, School of Nutrition and Translational Research in Metabolism, Maastricht University, Universiteitssingel 40 (Room C5.570), 6229 ER, Maastricht, the Netherlands., Department of Complex Genetics and Epidemiology, School of Nutrition and Translational Research in Metabolism, Maastricht University, Universiteitssingel 40 (Room C5.570), 6229 ER, Maastricht, the Netherlands. ., Department of Data Science and Knowledge Engineering, Maastricht University, Maastricht, The Netherlands., Department of General Practice, Katholieke Universiteit Leuven, ACHG-KU Leuven, Leuven, Belgium., Department of Epidemiology, Schools for Oncology and Developmental Biology and Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, The Netherlands., Department of Epidemiology Radiation Effects Research Foundation, Hiroshima, Japan., Fred Hutchinson Cancer Research Center, Seattle, WA, USA., International Agency for Research on Cancer World Health Organization, Lyon, France., Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK., Danish Cancer Society Research Center, Copenhagen, Denmark., Molecular and Lifestyle Epidemiology Branch, Cancer Risk Factors and Lifestyle Epidemiology Unit, Institute for Cancer Research, Prevention and Clinical Network ISPRO, Florence, Italy., Cancer Epidemiology Division, Cancer Council Victoria, 615 St Kilda Road, Melbourne, Victoria, 3004, Australia.