Consumption of Processed Meat and Unprocessed Red Meat and Risk of Bladder Cancer: A Pooled Analysis of 30 Cohort Studies.

Background

Processed meat and unprocessed red meat are considered carcinogenic and 'probably carcinogenic' to humans, respectively, but findings for bladder cancer remain inconsistent.

Objectives

We assessed associations between processed meat and unprocessed red meat intake and bladder cancer risk using data from the Pooling Project of Prospective Studies of Diet and Cancer.

Methods

Associations with bladder cancer risk were assessed using individual-level data from 30 cohort studies from North America, Europe, Australia and Asia. Diet was assessed at enrolment using validated food frequency questionnaires or diet histories. Following a pre-specified analysis plan, study- and sex-specific hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox regression, adjusted for smoking status and duration and other potential confounders, and pooled using inverse-variance-weighted random-effects meta-analysis.

Results

During median follow-up across cohorts of 8-29 years, among 2,575,971 participants, 20,780 were diagnosed with bladder cancer. Processed meat intake was associated with increased bladder cancer risk (HR comparing ≥40 with <5 g/day = 1.08; 95% CI: 1.02-1.15; HR per 20 g/day = 1.02; 95% CI: 1.00-1.03). Weaker evidence of association with increased risk was also observed for unprocessed red meat (HR comparing ≥100 with <20 g/day = 1.06; 95% CI: 1.00-1.13; HR per 50 g/day = 1.01; 95% CI: 0.99-1.03). There was no evidence of heterogeneity by study, sex, or region.

Conclusions

Higher intakes of processed meat and unprocessed red meat were associated with a small increase in risk of bladder cancer. These findings are consistent with existing public health recommendations to limit consumption of red and processed meat.