Urinary Bladder Cancer Risk Among Motor Vehicle Drivers: A Meta-analysis of the Evidence, 1977-2008

Background: The aim of the study was to summarize bladder cancer risk in motor vehicle drivers andrailroad workers using meta-analysis techniques.
Methods: We retrieved all published results (3 cohort studiesand 27 case-control studies) during 1977-2008. We assessed the heterogeneity of the results assuming a fixedeffectmodel. For cohort studies, the observed and the expected number of cases were added, respectively, toyield pooled observed/expected ratio. For case-control studies, we calculated pooled odds ratio (OR) andcorresponding 95% confidence interval (CI) as a weighted average of the ORs in each study, by giving a weightproportional to the inverse of the variance of the ORs.
Results: No overall meta-analysis was performed becauseof heterogeneity in results. The overall pooled risk among motor vehicle and railroad workers based on allcohort studies was 1.08 (95%: 1.00-1.17). The overall pooled risk among truck drivers was 1.18 (95% CI: 1.09-1.28 based on 18 case-control studies). The stratified analysis by year of publication indicated that pooled riskamong truck drivers was 1.20 (95% CI: 1.00-1.40) for the period 1998-2008. The corresponding risk for theperiod 1977-1987 was 1.30 (95%: 1.16-1.46). The overall pooled risk among bus drivers was 1.23 (95% CI: 1.06-1.44 based on 10 case-control studies). The pooled risk among bus drivers was 1.21 (95% CI: 0.72-2.01) for theperiod 1998-2008 and the corresponding risk for the period 1977-1987 was 1.30 (95%CI: 1.10-1.53). The pooledrisk among railroad workers was 1.20 (95% CI: 1.02-1.41 based on 15 case-control studies). Stratified analysisby year of publication was not statistically significant among railroad workers.
Conclusion: The pooled analysissuggested an increased bladder cancer risk among motor vehicle drivers and railroad workers. However, therisk among these workers is reduced in recent publications compared to the earlier publications.