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. 2017 Jan 23:7:693.
doi: 10.3389/fphys.2016.00693. eCollection 2016.

Tea Consumption and Risk of Bladder Cancer: A Dose-Response Meta-Analysis

Hong Weng  1 , Xian-Tao Zeng  1 , Sheng Li  1 , Joey S W Kwong  2 , Tong-Zu Liu  3 , Xing-Huan Wang  1
Affiliations

Tea Consumption and Risk of Bladder Cancer: A Dose-Response Meta-Analysis

Hong Weng et al. Front Physiol. .

Abstract

Background and Objective: Controversial results of the association between tea (black tea, green tea, mate, and oolong tea) consumption and risk of bladder cancer were reported among epidemiological studies. Thus, we performed a meta-analysis of observational studies to investigate the association. Methods: We searched the PubMed and Embase for studies of tea consumption and bladder cancer that were published in any language up to March, 2016. Cohort or case-control studies were included in the meta-analysis. All statistical analyses were performed in Stata 12.0 software. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relationship between tea consumption and risk of bladder cancer. Results: Totally, 25 case-control studies (15 643 cases and 30 795 controls) and seven prospective cohort studies (1807 cases and 443 076 participants) were included. The meta-analysis showed that tea consumption was not significantly associated with bladder cancer risk (OR = 0.96, 95% CI 0.86-1.06) (in a comparison of highest vs. lowest category). No non-linearity association was observed between tea consumption and bladder cancer risk (P = 0.51 for non-linearity). Specific analysis for black tea, green tea, and mate yielded similar results. The dose-response analysis showed the summary OR for an increment of 1 cup/day of tea consumption was 1.01 (95% CI 0.97-1.05). Conclusion: Results based on current meta-analysis indicated that no significant association was observed between tea consumption and risk of bladder cancer.

Keywords: bladder cancer; dose-response; meta-analysis; risk factor; tea consumption.

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Figures

Figure 1
Figure 1
Flow diagram of literature search and study selection.
Figure 2
Figure 2
The forest plot of tea consumption and the risk of bladder cancer.
Figure 3
Figure 3
The dose-response analysis of tea consumption and the risk of bladder cancer. The black solid line and the black long dashed line represent the estimated RRs and corresponding 95% CIs for the non-linearity. The red solid line and the red short dashed line represent the estimated RRs and corresponding 95% CIs for the linearity.
Figure 4
Figure 4
The forest plot of black tea consumption and the risk of bladder cancer.
Figure 5
Figure 5
The dose-response analysis of black tea consumption and the risk of bladder cancer. The black solid line and the black long dashed line represent the estimated RRs and corresponding 95% CIs for the non-linearity. The red solid line and the red short dashed line represent the estimated RRs and corresponding 95% CIs for the linearity.
Figure 6
Figure 6
The forest plot of green tea consumption and the risk of bladder cancer.
Figure 7
Figure 7
The dose-response analysis of green tea consumption and the risk of bladder cancer. The black solid line and the black long dashed line represent the estimated RRs and corresponding 95% CIs for the non-linearity. The red solid line and the red short dashed line represent the estimated RRs and corresponding 95% CIs for the linearity.
Figure 8
Figure 8
Sensitivity analysis of tea consumption and risk of bladder cancer.
Figure 9
Figure 9
Funnel plot for tea consumption and risk of bladder cancer.
Figure 10
Figure 10
Funnel plot for black tea consumption and risk of bladder cancer.
Figure 11
Figure 11
Funnel plot for green tea consumption and risk of bladder cancer.
See this image and copyright information in PMC

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