Cotton dust exposure and risk of lung cancer: A meta-analysis of observational studies

Findings on the association between cotton dust exposure and lung cancer risk in epidemiologic studies have been inconsistent. Therefore, we conducted a meta-analysis of data from observational studies to quantify this association. PubMed, EMBASE, and the Cochrane library databases were searched for observational studies with data on cotton dust exposure and lung cancer risk. Studies that reported adjusted relative risks (RRs) with 95% confidence intervals (CIs) of lung cancer associated with cotton dust exposure were included. Subgroup analyses were conducted according to key characteristics. Fifteen studies involving a total of 73,812 individuals were included in the meta-analysis. Combining estimates from all the 15 observational studies, cotton dust exposure was associated with a decreased risk of lung cancer (combined RR, 0.78; 95% CI, 0.66–0.91; P = .002). Pooled estimates of multivariate RRs by gender were 0.71 (95% CI, 0.58–0.88; P = .001) among males, based on 7 studies, and 0.77 (95% CI, 0.67–0.89; P < .001) among females, based on 9 studies. Further analyses examining the influence of a single study on the results by omitting a study at each turn yielded a range of RR from 0.74 to 0.82. Our meta-analysis indicates that cotton dust exposure is associated with a decreased risk of lung cancer.