Occupational variation in incidence of bladder cancer: a comparison of population-representative cohorts from Nordic countries and Canada

Hadkhale K, MacLeod J, Demers PA, Martinsen JI, Weiderpass E, Kjaerheim K, Lynge E, Sparen P, Tryggvadottir L, Harris MA, Tjepkema M, Peters PA, Pukkala E. Occupational variation in incidence of bladder cancer: a comparison of population-representative cohorts from Nordic countries and Canada. BMJ Open. 2017;7(8):e016538. doi:10.1136/bmjopen-2017-016538

Objectives: The objective of this study was to compare occupational variation of the risk of bladder cancer in the Nordic countries and Canada.

Methods: In the Nordic Occupational Cancer study (NOCCA), 73 653 bladder cancer cases were observed during follow-up of 141.6 million person-years. In the Canadian Census Health and Environment Cohort (CanCHEC), 8170 cases were observed during the follow-up of 36.7 million person-years. Standardised incidence ratios with 95% CI were estimated for 53 occupations in the NOCCA cohort and HR with 95% CIs were estimated for 42 occupations in the CanCHEC.

Results: Elevated risks of bladder cancer were observed among hairdressers, printers, sales workers, plumbers, painters, miners and laundry workers. Teachers and agricultural workers had reduced risk of bladder cancer in both cohorts. Chimney-sweeps, tobacco workers and waiters had about 1.5-fold risk in the Nordic countries; no risk estimates for these categories were given from the CanCHEC cohort.

Conclusion: We observed different occupational patterns in risk of bladder cancer in Nordic countries and Canada. The only occupation with similarly increased risk was observed among sales workers. Differences in smoking across occupational groups may explain some, but not all, of this variation.