Abstract
BackgroundAlthough 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.MethodsVegetable 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.ResultsThe 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.ConclusionHigher 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.
Highlights
A potential inverse association between vegetable intake and bladder cancer risk has been reported, epidemiological evidence is inconsistent
Higher intakes of total and non-starchy vegetable are associated with reduced risk of bladder cancer for women
Higher intake of total vegetable, non-starchy vegetables, green leafy vegetable and cruciferous vegetable were observed in bladder cancer cases (P value < 0.001, < 0.001, 0.476 and < 0.001 respectively), while only higher intake of starchy vegetables was observed in non-bladder-cancer cases (P value < 0.001)
Summary
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. Bladder cancer is the most common malignancy of urinary tract, with an estimated 550,000 new cases and 200, 000 deaths annually [1,2,3]. Incidence rates of bladder cancer are highest in Europe and North America, with a strong predominance in men and the elderly [4,5,6,7,8,9]. Due to its high rate of recurrence, bladder cancer places costly burden on healthcare systems in terms of life time treatment [10]. The World Cancer Research Fund (WCRF) International’s Continuous Update Project (CUP) 2018 [19] found that the evidence suggesting that higher intake of vegetable decreases the risk of bladder cancer is limited
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