A meta-analysis on the association between bladder cancer and occupation

To date, many epidemiological studies have been conducted to examine the association between occupation and bladder cancer incidence. However, results from these studies often have been inconsistent, and significant associations have rarely been found, possibly owing to the lack of adequate statistical power in these studies. This meta-analysis summarizes the relevant literature regarding occupation and bladder cancer incidence to increase the statistical power to detect associations. The Medline and Embase databases were searched to retrieve epidemiological studies published up until May 2008. Individual risk estimates for subjects with an employment history in the occupation of interest were extracted from each included publication. For each occupation, a summary relative risk (SRR) was calculated by means of a random effects model. Significantly increased risks with an SRR greater than 1.20 were identified for miners [SRR=1.31, 95% confidence interval (CI) 1.09-1.57], bus drivers (SRR=1.29, 95% CI 1.08-1.53), rubber workers (SRR=1.29, 95% CI 1.06-1.58), motor mechanics (SRR=1.27, 95% CI 1.10-1.46), leather workers (SRR=1.27, 95% CI 1.07-1.49), blacksmiths (SRR=1.27, 95% CI 1.02-1.58), machine setters (SRR=1.24, 95% CI 1.09-1.42), hairdressers (SRR=1.23, 95% CI 1.11-1.37) and mechanics (SRR=1.21, 95% CI 1.12-1.31). In conclusion, the studies reviewed provide consistent support for a small but significant increased risk of bladder cancer among workers in these nine occupations. Although the relative risk of bladder cancer associated with these occupations is small, the public health impact may be significant, considering the substantial number of people who were and are employed in these occupations.