Lee C. Yong

PURPOSE: Lung cancer is a leading cause of cancer death worldwide. Although smoking remains the predominant cause of lung cancer, lung cancer in never smokers is an increasingly prominent public health issue. However, data on this topic, particularly lung cancer incidence rates in never smokers, are limited. METHODS: We reviewed the existing literature on lung cancer incidence and mortality rates among never smokers and present new data regarding rates in never smokers from the following large, prospective cohorts: Nurses' Health Study; Health Professionals Follow-Up Study; California Teachers Study; Multiethnic Cohort Study; Swedish Lung Cancer Register in the Uppsala/Orebro region; and First National Health and Nutrition Examination Survey Epidemiologic Follow-Up Study. RESULTS: Truncated age-adjusted incidence rates of lung cancer among never smokers age 40 to 79 years in these six cohorts ranged from 14.4 to 20.8 per 100,000 person-years in women and 4.8 to 13.7 per 100,000 person-years in men, supporting earlier observations that women are more likely than men to have non-smoking-associated lung cancer. The distinct biology of lung cancer in never smokers is apparent in differential responses to epidermal growth factor receptor inhibitors and an increased prevalence of adenocarcinoma histology in never smokers. CONCLUSION: Lung cancer in never smokers is an important public health issue, and further exploration of its incidence patterns, etiology, and biology is needed.

OBJECTIVE: To estimate the prevalence of a comprehensive set of self-reported sleep problems by job characteristics, including shiftwork status, among a representative sample of US workers. METHODS: Data for 6338 workers aged ≥18 years were obtained from the National Health and Nutrition Examination Survey. Short sleep duration was defined as <7 hours per weekday/workday. Sleep quality was categorised as good, moderate and poor based on the frequency of 6 sleep-related symptoms. A sleep-related activities of daily living (ADL) score ≥2 was defined as impaired. Insomnia was defined as having poor sleep quality and impaired ADL. Shiftwork status was categorised as daytime, night, evening, rotating or another schedule. Prevalence rates were calculated and multivariate logistic regression analyses were used. RESULTS: The prevalence of short sleep duration (37.6% overall) was highest among night shift workers (61.8%; p<0.001). The prevalence of poor sleep quality was 19.2% among all workers, with the highest prevalence among night shift workers (30.7%, p=0.004). The prevalence of impaired ADL score (24.8% overall) and insomnia (8.8% overall) was also highest for night shift workers (36.2%, p=0.001 and 18.5%, p=0.013, respectively). In multivariate analysis, night shift workers had the highest likelihood of these sleep problems. CONCLUSIONS: Self-reported short sleep duration, poor sleep quality, impaired ADL score and insomnia are common among US workers especially among night shift workers. Although these findings should be confirmed with objective sleep measures, they support the need for intervention programmes to improve sleep quantity and quality among night shift workers.

The U.S. population has nearly one radiographic examination per person per year, and concern about cancer risks associated with medical radiation has increased. Radiologic technologists were surveyed to determine whether their personal cumulative exposure to diagnostic X-rays was associated with increased frequencies of chromosome translocations, an established radiation biomarker and possible intermediary suggesting increased cancer risk. Within a large cohort of U.S. radiologic technologists, 150 provided a blood sample for whole chromosome painting and were interviewed about past X-ray examinations. The number and types of examinations reported were converted to a red bone marrow (RBM) dose score with units that approximated 1 mGy. The relationship between dose score and chromosome translocation frequency was assessed using Poisson regression. The estimated mean cumulative RBM radiation dose score was 49 (range, 0-303). After adjustment for age, translocation frequencies significantly increased with increasing RBM dose score with an estimate of 0.004 translocations per 100 cell equivalents per score unit (95% confidence interval, 0.002-0.007; P < 0.001). Removing extreme values or adjustment for gender, cigarette smoking, occupational radiation dose, allowing practice X-rays while training, work with radioisotopes, and radiotherapy for benign conditions did not affect the estimate. Cumulative radiation exposure from routine X-ray examinations was associated independently with increased chromosome damage, suggesting the possibility of elevated long-term health risks, including cancer. The slope estimate was consistent with expectation based on cytogenetic experience and atomic bomb survivor data.

Ethylene oxide (EtO) is a genotoxic carcinogen with widespread uses as an industrial chemical intermediate and sterilant. We examined the effects of glutathione S-transferase T1 (GSTT1) and M1 (GSTM1) genotypes on the levels of N-(2-hydroxyethyl)valine (HEV) adducts in the erythrocytes and sister chromatid exchange (SCE) in lymphocytes from a group of 58 operators of sterilizers that used EtO and nonexposed workers from nine hospitals in the United States and one hospital in Mexico City. Cumulative exposure to EtO was estimated during the 4-month period before the collection of blood samples. Results showed that EtO exposure was significantly associated with the levels of HEV adducts and SCE after adjusting for cigarette smoking and other potential confounders. A significantly higher HEV adduct level (0.17 +/- 0.03 versus 0.08 +/- 0.01, mean +/- SE; P = 0.02) but lower SCE frequency (5.31 +/- 0.39 versus 6.21 +/- 0.17; P = 0.04) was observed in subjects with homozygous deletion of the GSTT1 gene (null genotype) as compared with those with at least one copy of the gene (positive genotype). In multiple regression analysis, the GSTT1-null genotype was associated with an increase in HEV adduct level (beta = 1.62; P = 0.02) and a decrease in SCE frequency (beta = -1.25; P = 0.003) after adjusting for age, gender, race, education, cigarette smoking, and EtO exposure status. The inverse SCE-GSTT1 relationship remained unchanged when SCE was further examined in relation to HEV adducts as an indicator of the internal EtO dose. The GSTM1 genotype was not associated with the level of either HEV adduct or SCE. These data indicate that the GSTT1-null genotype is associated with increased formation of EtO-hemoglobin adducts in relation to occupational EtO exposure, suggesting that individuals with homozygous deletion of the GSTT1 gene may be more susceptible to the genotoxic effects of ETO: The unexpected finding of decreased SCEs, which is less clear, may be attributed to the nonchemical specificity of this end point and the lack of expression of the GSTT1 enzyme in lymphocytes.