Anti-inflammatory Diet Index and Bladder Cancer Risk by Stage: A 22-Year Prospective Swedish Cohort Study (1998-2020)

Dietary patterns influencing systemic levels of inflammation have been proposed and investigated as possible determinants of cancer risk. We evaluated the association between the anti-inflammatory potential of diet and the risk of bladder cancer.

The anti-inflammatory diet index (AIDI), composed of 16 food groups (11 anti- and 5 pro-inflammatory), was used to score dietary patterns in N = 79,292 individuals derived from the Cohort of Swedish Men (established in 1997) and the Swedish Mammography Cohort (established in 1987). Dietary information was collected in 1997 and 2009; repeated-measures analyses used a cumulative-average AIDI. Incident bladder cancer cases were identified from the Swedish Cancer Register using International Classification of Diseases, 10th Revision code C67, and a baseline study questionnaire was used to assess covariates. We estimated multivariable hazard ratios (HR) across AIDI quartiles using Cox models.

After a 22-year follow-up, 1,165 individuals were diagnosed with bladder cancer, of whom 249 had non-muscle invasive bladder cancer (NMIBC), 201 had muscle-invasive bladder cancer (MIBC), and 715 had unknown stage. In repeated-measures analyses, the highest anti-inflammatory quartile (Q4) was associated with lower bladder cancer risk compared with the lowest quartile [Q1; HR, 0.74; 95% confidence interval (CI), 0.61-0.89]. Stratifying for tumor stage, there was a clear association between AIDI score and MIBC (HR, 0.35; 95% CI, 0.22-0.57) but not for NMIBC (HR, 0.86; 95% CI, 0.57-1.28).

An anti-inflammatory dietary pattern was associated with lower bladder cancer risk, with the clearest association for MIBC.

These findings support the role of dietary inflammation in bladder cancer etiology and suggest that promoting anti-inflammatory dietary patterns could contribute to cancer prevention strategies.