Risk for lung cancer in workers exposed to benzidine and/or beta-naphthylamine: a protocol for systematic review and meta-analysis

Risk of Lung Cancer in Workers Exposed to Benzidine and/or Beta-Naphthylamine: A Systematic Review and Meta-Analysis

Benzidine (BZ) and beta-naphthylamine (BNA) have been classified as definite human carcinogens for bladder cancer by the International Agency for Research on Cancer. However, the epidemiological evidence for an association between exposure to BZ and/or BNA and lung cancer has been inconclusive. We conducted a systematic review and meta-analysis to determine the risk for lung cancer among workers exposed to BZ/BNA. A systematic literature search was conducted to identify studies that had reported occupational BZ/BNA exposure and the outcome of interest (lung cancer death and/or incidence). Meta-analyses were performed using random effects models to combine standardized mortality ratios (SMRs) or standardized incidence ratios (SIRs). We identified 23 retrospective cohort studies including 1745 cases of lung cancer; only one study reported smoking-adjusted lung cancer risk. A significantly increased lung cancer risk (pooled SMR/SIR 1.28; 95% CI, 1.14-1.43) was observed by combining all studies, with significant heterogeneity among studies (I(2) = 64.1%, P < 0.001). Effect estimates were higher for studies with direct BZ/BNA exposure (ie, dyestuff and manufacturing industries) (pooled SMR/SIR 1.58; 95% CI, 1.31-1.89), and studies that identified BZ/BNA-associated bladder cancer with SMR/SIR ≥4.7 (pooled SMR/SIR 1.68; 95% CI, 1.35-2.09). Effect estimates were similar for studies with and without concomitant occupational exposure to chromium, asbestos, arsenic, or bis(chloromethyl) ether. The cumulative meta-analysis showed that the evidence of association between occupational BZ/BNA exposure and lung cancer has been stable since 1995. Although the results of this meta-analysis have the potential for confounding by smoking and heterogeneity, our findings suggest that a finding of lung cancer following occupational BZ/BNA exposure should be considered to be a potential occupational disease.

Coffee consumption and the risk of lung cancer: an updated meta-analysis of epidemiological studies

BACKGROUND/OBJECTIVES

Coffee is one of the most popularly consumed beverages worldwide. Many epidemiological studies have investigated the association between coffee consumption and lung cancer risk, but the results are inconsistent. Hence, we conducted a systematic analysis of relevant population-based studies to examine this association and derive a more precise estimation.

SUBJECTS/METHODS

The Cochrane library, PubMed and Embase databases were searched to identify studies published through Mar 2015 that met the predetermined inclusion criterion. Seventeen studies (5 cohort and 12 case-control studies) involving 12 276 cases and 102 516 controls were included.

RESULTS

The summary odds ratio (OR) of lung cancer was 1.17 (95% confidence interval (CI): 1.03-1.33) for coffee drinkers compared with nondrinkers and 1.31 (95% CI: 1.11-1.55) for the highest category of coffee consumption compared with the lowest category. Compared with nondrinkers, the pooled ORs for lung cancer were 1.10 (95% CI: 0.92-1.31) for ⩽1 cup per day, 1.10 (95% CI: 0.93-1.30) for 2-3 cups per day and 1.20 (95% CI: 1.02-1.39) for ⩾3 cups per day. Further analysis showed that the ORs for hospital-based case-control studies, population-based case-control studies and prospective cohort studies were 1.36 (95% CI: 1.10-1.69), 0.99 (95% CI: 0.77-1.28) and 1.59 (95% CI: 1.26-2.00), respectively. Significant associations for high coffee intake with increased risk of lung cancer were observed in men (OR=1.41 95% CI: 1.21-1.63), but not in women (OR=1.16, 95% CI: 0.86-1.56), in American (OR=1.34 95% CI: 1.08-1.65) and Asian populations (OR=1.49 95% CI: 1.28-1.74), but not in European populations (OR=1.12, 95% CI: 0.74-1.67), and in smokers (OR=1.24, 95% CI: 1.00-1.54), but not in nonsmokers (OR=0.85, 95% CI: 0.64-1.11). Particularly over the last 5 years, studies have consistently indicated that lung cancer risk is significantly increased by 47% in the population with the highest category intake of coffee compared with that with the lowest category intake (OR=1.47, 95% CI: 1.21-1.79).

CONCLUSION

The present study suggested that coffee intake was associated with an increased risk of lung cancer.