Epidemiol Health. 2021 Sep 8:e2021057. doi: 10.4178/epih.e2021057. Online ahead of print.
ABSTRACT
OBJECTIVES: To compare meta-analysis results with and without adjustment for healthy worker effect on the association between working in the semiconductor industry and cancer mortality.
METHODS: A total of six studies that reported standardized mortality ratios (SMRs) for cancers were selected for meta-analysis. The SMR results from individual study were combined for all cancers, leukemia and lymphoma to estimate the summary SMRs and 95% confidence intervals (CIs) with random-effects model. To adjust for healthy worker effect, the relative SMRs (rSMR=SMRx/SMRnot x) were calculated using observed and expected counts for the specific cause of interest (i.e., all cancers and leukemia) and observed and expected counts for all the other causes of mortality. Then, the rSMR results were combined to estimate the summary rSMRs and 95% confidence intervals.
RESULTS: The SMRs for all causes among semiconductor industry workers ranged from 0.25 to 0.80, which reflects significant healthy worker effects. Remarkable difference was found between the summary SMRs and the summary rSMRs. The summary SMR for all cancers was 0.70 (95% CI=0.63-0.79) whereas the summary rSMR was 1.38 (1.20-1.59). The summary SMR for leukemia was 0.88 (0.72-1.08), and the summary rSMR was 1.38 (1.20-1.59).
CONCLUSION: Our results suggest that the adjustment for the healthy worker effect (i.e., rSMR) may be useful in meta-analyses of cohort studies reporting SMRs.
PMID:34525505 | DOI:10.4178/epih.e2021057
