Presenter/Creator Information

Sherman Selix, Yale UniversityFollow

Description

Petroleum refineries employ a variety of workers who historically experienced different potentials for asbestos exposure depending on job tasks. Associations between petroleum refinery work and lung cancer related to occupational asbestos exposure have been quantified among various locations, corporations, and time periods. To combine the data from several individual refinery studies and examine an overall effect, a systematic review and stratified meta-analysis was employed. Using set search terms among four databases, 112 potential publications were identified, of which 29 qualified for meta-analysis. Risk estimates and confidence intervals were extracted from these publications to construct four separate datasets. Inverse variance weighting assuming random effects was used to combine Standardized Mortality and Incidence data separately for all male and female refinery workers, as well as both standardized and relative risk measurements for the subset of male maintenance workers, who may have been exposed to higher levels. Males in cohorts consisting of all refinery workers, which included both blue and white collar workers, had a meta-Risk Ratio (mRR) of 0.80 (95% CI: 0.75-0.85) when compared to population controls, all female refinery workers had an mRR of 1.27 (95% CI: 0.86-1.87) when compared to population controls, a statistically significant difference. Male maintenance workers exhibited an mRR of 0.88 (95% CI: 0.74-1.04) with population controls, and an mRR of 1.62 (95% CI: 1.30-2.02) when internally compared to other refinery workers. This large differential in risk estimates for the same population could be related to sampling biases in opposite directions: population controls are subject to the “healthy worker effect”, while internal comparisons may differ from maintenance workers in both socio-economics and smoking rates. Due these potentially confounded and conflicting results, no conclusion could be drawn regarding lung cancer risk for refinery workers. Accurate quantification of lung cancer risk for refinery workers will depend on addressing these issues.

Keywords: Biostatistics, Meta-analysis, Risk, Epidemiology, Review, Database, Cancer, Asbestos, Bias, Confounding

 

Stratified Meta-Analysis to Examine Data Biases in Lung Cancer Studies of Refinery Workers

Petroleum refineries employ a variety of workers who historically experienced different potentials for asbestos exposure depending on job tasks. Associations between petroleum refinery work and lung cancer related to occupational asbestos exposure have been quantified among various locations, corporations, and time periods. To combine the data from several individual refinery studies and examine an overall effect, a systematic review and stratified meta-analysis was employed. Using set search terms among four databases, 112 potential publications were identified, of which 29 qualified for meta-analysis. Risk estimates and confidence intervals were extracted from these publications to construct four separate datasets. Inverse variance weighting assuming random effects was used to combine Standardized Mortality and Incidence data separately for all male and female refinery workers, as well as both standardized and relative risk measurements for the subset of male maintenance workers, who may have been exposed to higher levels. Males in cohorts consisting of all refinery workers, which included both blue and white collar workers, had a meta-Risk Ratio (mRR) of 0.80 (95% CI: 0.75-0.85) when compared to population controls, all female refinery workers had an mRR of 1.27 (95% CI: 0.86-1.87) when compared to population controls, a statistically significant difference. Male maintenance workers exhibited an mRR of 0.88 (95% CI: 0.74-1.04) with population controls, and an mRR of 1.62 (95% CI: 1.30-2.02) when internally compared to other refinery workers. This large differential in risk estimates for the same population could be related to sampling biases in opposite directions: population controls are subject to the “healthy worker effect”, while internal comparisons may differ from maintenance workers in both socio-economics and smoking rates. Due these potentially confounded and conflicting results, no conclusion could be drawn regarding lung cancer risk for refinery workers. Accurate quantification of lung cancer risk for refinery workers will depend on addressing these issues.

Keywords: Biostatistics, Meta-analysis, Risk, Epidemiology, Review, Database, Cancer, Asbestos, Bias, Confounding