Incidence of cancer among female flight attendants: a meta-analysis

The contribution of circadian clock to the biological processes

All organisms have various circadian, behavioral, and physiological 24-h periodic rhythms, which are controlled by the circadian clock. The circadian clock controls various behavioral and physiological rhythms. In mammals, the primary circadian clock is present in the suprachiasmatic nucleus of the hypothalamus. The rhythm of the circadian clock is controlled by the interaction between negative and positive feedback loops, consisting of crucial clock regulators (including Bmal1 and Clock), three cycles (mPer1, mPer2, and mPer3), and two cryptochromes (Cry1 and Cry2). The development of early mammalian embryos is an ordered and complex biological process that includes stages from fertilized eggs to blastocysts and undergoes important morphological changes, such as blastocyst formation, cell multiplication, and compaction. The circadian clock affects the onset and timing of embryonic development. The circadian clock affects many biological processes, including eating time, immune function, sleep, energy metabolism, and endocrinology, therefore, it is also crucial for overall health, growth and development after birth. This review summarized the effects of the circadian clock in the body's physiological activities. A new strategy is proposed for the prevention of malformations or diseases by regulating the circadian clock or changing circadian rhythms.

Assessment of risks for breast cancer in a flight attendant exposed to night shift work and cosmic ionizing radiation: a case report

Background

Some epidemiological studies have estimated exposure among flight attendants with and without breast cancer. However, it is difficult to find a quantitative evaluation of occupational exposure factors related to cancer development individually in the case of breast cancer in flight attendants. That is, most, if not all, epidemiological studies of breast cancer in flight attendants with quantitative exposure estimates have estimated exposure in the absence of individual flight history data.

Case presentation

A 41-year-old woman visited the hospital due to a left breast mass after a regular check-up. Breast cancer was suspected on ultrasonography. Following core biopsy, she underwent various imaging modalities. She was diagnosed invasive ductal carcinoma of no special type (estrogen receptor positive in 90%, progesterone receptor positive in 3%, human epidermal growth factor receptor 2/neu equivocal) with histologic grade 3 and nuclear grade 3 in the left breast. Neoadjuvant chemotherapy was administered to reduce the tumor size before surgery. However, due to serious chemotherapy side effects, the patient opted for alternative and integrative therapies. She joined the airline in January, 1996. Out of all flights, international flights and night flights accounted for 94.9% and 26.2, respectively. Night flights were conducted at least four times per month. Moreover, based on the virtual computer program CARI-6M, the estimated dose of cosmic radiation exposure was 78.81 mSv. There were no other personal triggers or family history of breast cancer.

Conclusions

This case report shows that the potentially causal relationship between occupational harmful factors and the incidence of breast cancer may become more pronounced when night shift workers who work continuously are exposed to cosmic ionizing radiation. Therefore, close attention and efforts are needed to adjust night shift work schedules and regulate cosmic ionizing radiation exposure.

Flight attendant occupational nutrition and lifestyle factors associated with COVID-19 incidence

In the era of COVID-19, essential workers are plagued with unforeseen and obfuscated challenges. Flight attendants are a unique subgroup of essential workers who face a multitude of health risks attributed to occupational exposures that are accentuated by the COVID-19 pandemic. Such risks can be ameliorated with strategies that target factors which enhance COVID-19 risk, including modifiable factors of diet and lifestyle. The aim of this cross-sectional study is to detect occupational dietary and lifestyle factors which could increase COVID-19 incidence amongst flight attendants. To identify potential risk factors, a questionnaire was administered to eighty-four flight attendants and examined the participants’ diet and lifestyle, and COVID-19 incidence. Descriptive statistics and logistic regression indicated that the participants’ perceived dietary quality at work (p = 0.003), sleep disruptions which impacted their consumption of a healthy diet (p = 0.013), job tenure (OR: 0.67, 95% CI: 0.46:0.98) and frequency of reported cold/flu (OR: 1.49, 95% CI: 1.014–2.189) were all factors associated with confirmed/suspected COVID-19 incidence. This study also revealed that a lack of infrastructure for food storage and time limitations are considerable occupational barriers for flight attendants to consume healthy foods. Additional investigation can further elucidate these relationships and related solutions to mitigate COVID-19 risk in the future.

Clock at the Core of Cancer Development

To synchronize various biological processes with the day and night cycle, most organisms have developed circadian clocks. This evolutionarily conserved system is important in the temporal regulation of behavior, physiology and metabolism. Multiple pathological changes associated with circadian disruption support the importance of the clocks in mammals. Emerging links have revealed interplay between circadian clocks and signaling networks in cancer. Understanding the cross-talk between the circadian clock and tumorigenesis is imperative for its prevention, management and development of effective treatment options. In this review, we summarize the role of the circadian clock in regulation of one important metabolic pathway, insulin/IGF1/PI3K/mTOR signaling, and how dysregulation of this metabolic pathway could lead to uncontrolled cancer cell proliferation and growth. Targeting the circadian clock and rhythms either with recently discovered pharmaceutical agents or through environmental cues is a new direction in cancer chronotherapy. Combining the circadian approach with traditional methods, such as radiation, chemotherapy or the recently developed, immunotherapy, may improve tumor response, while simultaneously minimizing the adverse effects commonly associated with cancer therapies.

Shift work and risk of skin cancer: A systematic review and meta-analysis

Shift work with circadian disruption has been considered as a carcinogenic risk factor for skin cancer. The few prior studies that investigated the association between shift work and skin cancer have inconclusive results. Our main objective was to evaluate the associations between shift work and the risks of different types of skin cancer. We systematically searched PubMed, Web of Science, Cochrane Library, EMBASE and Science Direct until October 2018 for studies that included a relationship between shift work and skin cancer. Our search yielded 193 articles and 9 studies met the criteria for our review. The included studies involved 3,579,147 participants and 17,308 skin cancer cases. Overall, ever shift work, was associated with increased risk of melanoma (RR = 1.10, 95% CI = 1.05–1.16) and a significant decrease in the risk of BCC (RR = 0.90, 95% CI = 0.88–0.93). No association between shift work and the risk of SCC was detected. Interestingly, our dose response analysis demonstrated that the risk of melanoma cumulatively increases by 2% for every year of shift work (RR = 1.02; 95% CI = 1.00–1.03). In conclusion, shift work is associated with increased risk of melanoma and deceased risk of BCC. Further studies are needed to confirm our findings and to elucidate the related potential biological mechanisms.

The Cancer Clock Is (Not) Ticking: Links between Circadian Rhythms and Cancer

Circadian rhythms regulate many physiological and behavioral processes, including sleep, metabolism and cell division, which have a 24-h oscillation pattern. Rhythmicity is generated by a transcriptional–translational feedback loop in individual cells, which are synchronized by the central pacemaker in the brain and external cues. Epidemiological and clinical studies indicate that disruption of these rhythms can increase both tumorigenesis and cancer progression. Environmental changes (shift work, jet lag, exposure to light at night), mutations in circadian regulating genes, and changes to clock gene expression are recognized forms of disruption and are associated with cancer risk and/or cancer progression. Experimental data in animals and cell cultures further supports the role of the cellular circadian clock in coordinating cell division and DNA repair, and disrupted cellular clocks accelerate cancer cell growth. This review will summarize studies linking circadian disruption to cancer biology and explore how such disruptions may be further altered by common characteristics of tumors including hypoxia and acidosis. We will highlight how circadian rhythms might be exploited for cancer drug development, including how delivery of current chemotherapies may be enhanced using chronotherapy. Understanding the role of circadian rhythms in carcinogenesis and tumor progression will enable us to better understand causes of cancer and how to treat them.

Cancer Incidence Among Air Transportation Industry Workers Using the National Cohort Study of Korea

Background: There are increasing concerns regarding increased cancer risks in professional flight attendants due to their exposure to occupational hazards that are known or suspected to be carcinogenic. In this study, we aimed to analyze various cancer risks among a cohort of Korean air transportation industry workers. Methods: We used data from the Korean National Health Insurance Service (NHIS) database from 2002 to 2015. The age-standardized incidence ratios (SIRs) for all types of cancers in the aircraft transport industry workers compared to government employees and the entire employee population were calculated with adjustment for five-year age ranges via the indirect standardized method with gender stratification. Results: Leukemia (ICD-10; C91–C95) showed significantly higher SIRs (95% confidence interval (CI)) compared to the government employee group (1.86, 1.15–2.84) and the whole employee group (1.77, 1.10–2.70). Conclusion: Air transportation industry workers have an increased risk of leukemia compared to other occupational groups.

Legacy health effects among never smokers exposed to occupational secondhand smoke

OBJECTIVES

Secondhand tobacco smoke (SHTS) is a tremendous public health hazard, leading to morbidity and premature mortality worldwide, with racial and ethnic minorities and those of lower socioeconomic status disproportionately affected. Flight attendants were historically exposed to high levels of SHTS in the aircraft cabin. The health effects of active smoking are known to persist for up to a lifetime, but the legacy effects of SHTS exposure have not been well characterized.

DESIGN

We aimed to evaluate the legacy health effects of occupational SHTS exposure among never smoking workers using the resources of the Harvard Flight Attendant Health Study, a large study of cabin crew health. We evaluated associations between SHTS exposure and a range of diagnoses using multivariate logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs), employing a case-control sampling method and applying the bootstrap method to increase accuracy and precision of results.

RESULTS

We found no evidence of positive associations between SHTS and any cancer, but observed associations between SHTS and cardiac outcomes, including myocardial infarction (OR = 140, 95% CI: 1·04, 3·27) and peripheral artery disease (OR = 1·27, 95% CI: 1·00, 1·97). We also found associations between SHTS exposure and repeated pneumonia (OR = 1·06, 95% CI: 1·02, 1·10).

CONCLUSIONS

Our study reports associations between legacy SHTS exposure going back decades and severe cardiac and respiratory health outcomes. Given the high prevalence of ongoing and historical SHTS exposure, our findings, if confirmed, have important implications for smoking cessation efforts, health education, and clinical guidelines.

Cancer prevalence among flight attendants compared to the general population

BACKGROUND

Flight attendants are an understudied occupational group, despite undergoing a wide range of adverse job-related exposures, including to known carcinogens. In our study, we aimed to characterize the prevalence of cancer diagnoses among U.S. cabin crew relative to the general population.

METHODS

In 2014-2015, we surveyed participants of the Harvard Flight Attendant Health Study. We compared the prevalence of their self-reported cancer diagnoses to a contemporaneous cohort in the National Health and Nutrition Examination Survey (NHANES 2013-2014) using age-weighted standardized prevalence ratios (SPRs). We also analyzed associations between job tenure and the prevalence of selected cancers, using logistic regression and adjusting for potential confounders.

RESULTS

Compared to NHANES participants with a similar socioeconomic status (n = 2729), flight attendants (n = 5366) had a higher prevalence of every cancer we examined, especially breast cancer, melanoma, and non-melanoma skin cancer among females. SPR for these conditions were 1.51 (95% CI: 1.02, 2.24), 2.27 (95% CI: 1.27, 4.06), and 4.09 (95% CI: 2.70, 6.20), respectively. Job tenure was positively related to non-melanoma skin cancer among females, with borderline associations for melanoma and non-melanoma skin cancers among males. Consistent with previous studies, we observed associations between job tenure and breast cancer among women who had three or more children.

CONCLUSIONS

We observed higher rates of specific cancers in flight attendants compared the general population, some of which were related to job tenure. Our results should be interpreted in light of self-reported health information and a cross-sectional study design. Future longitudinal studies should evaluate associations between specific exposures and cancers among cabin crew.

Estimating the health consequences of flight attendant work: comparing flight attendant health to the general population in a cross-sectional study

BACKGROUND

Flight attendants are an understudied occupational group, despite undergoing a wide and unique range of adverse job-related exposures. In our study, we aimed to characterize the health profile of cabin crew relative to the U.S. general population.

METHODS

In 2014-2015, we surveyed participants of the Harvard Flight Attendant Health Study. We compared the prevalence of their health conditions to a contemporaneous cohort in the National Health and Nutrition Examination Survey (NHANES 2013-2014) using age-weighted standardized prevalence ratios (SPRs). We also analyzed associations between job tenure and selected health outcomes, using logistic regression and adjusting for potential confounders.

RESULTS

Compared to the NHANES population (n = 2729), flight attendants (n = 5366) had a higher prevalence of female reproductive cancers (SPR = 1.66, 95% CI: 1.18-2.33), cancers at all sites (SPR = 2.15, 95% CI: 1.73-2.67 among females), as well as sleep disorders, fatigue, and depression, with SPRs ranging between 1.98 and 5.57 depending on gender and the specific condition examined. In contrast, we observed a decreased prevalence of cardiac and respiratory outcomes among flight crew relative to NHANES. Health conditions that increased with longer job tenure were sleep disorders, anxiety/depression, alcohol abuse, any cancer, peripheral artery disease, sinusitis, foot surgery, infertility, and several perinatal outcomes.

CONCLUSIONS

We observed higher rates of specific adverse health outcomes in U.S. flight attendants compared to the general population, as well as associations between longer tenure and health conditions, which should be interpreted in light of recall bias and a cross-sectional design. Future longitudinal studies should evaluate specific exposure-disease associations among flight crew.

Association between light at night, melatonin secretion, sleep deprivation, and the internal clock: Health impacts and mechanisms of circadian disruption

Exposure to Artificial Light At Night (ALAN) results in a disruption of the circadian system, which is deleterious to health. In industrialized countries, 75% of the total workforce is estimated to have been involved in shift work and night work. Epidemiologic studies, mainly of nurses, have revealed an association between sustained night work and a 50-100% higher incidence of breast cancer. The potential and multifactorial mechanisms of the effects include the suppression of melatonin secretion by ALAN, sleep deprivation, and circadian disruption. Shift and/or night work generally decreases the time spent sleeping, and it disrupts the circadian time structure. In the long run, this desynchronization is detrimental to health, as underscored by a large number of epidemiological studies that have uncovered elevated rates of several diseases, including cancer, diabetes, cardiovascular risks, obesity, mood disorders and age-related macular degeneration. It amounts to a public health issue in the light of the very substantial number of individuals involved. The IARC has classified shift work in group 2A of "probable carcinogens to humans" since "they involve a circadian disorganization". Countermeasures to the effects of ALAN, such as melatonin, bright light, or psychotropic drugs, have been proposed as a means to combat circadian clock disruption and improve adaptation to shift and night work. We review the evidence for the ALAN impacts on health. Furthermore, we highlight the importance of an in-depth mechanistic understanding to combat the detrimental properties of exposure to ALAN and develop strategies of prevention.

Modifiable risk factors for the prevention of bladder cancer: a systematic review of meta-analyses

Each year, 430,000 people are diagnosed with bladder cancer. Due to the high recurrence rate of the disease, primary prevention is paramount. Therefore, we reviewed all meta-analyses on modifiable risk factors of primary bladder cancer. PubMed, Embase and Cochrane database were systematically searched for meta-analyses on modifiable risk factors published between 1995 and 2015. When appropriate, meta-analyses (MA) were combined in meta-meta-analysis (MMA). If not, the most comprehensive MA was selected based on the number of primary studies included. Probability of causation was calculated for individual factors and a subset of lifestyle factors combined. Of 1496 articles identified, 5 were combined in MMA and 21 were most comprehensive on a single risk factor. Statistically significant associations were found for current (RR 3.14) or former (RR 1.83) cigarette smoking, pipe (RR 1.9) or cigar (RR 2.3) smoking, antioxidant supplementation (RR 1.52), obesity (RR 1.10), higher physical activity levels (RR 0.86), higher body levels of selenium (RR 0.61) and vitamin D (RR 0.75), and higher intakes of: processed meat (RR 1.22), vitamin A (RR 0.82), vitamin E (RR 0.82), folate (RR 0.84), fruit (RR 0.77), vegetables (RR 0.83), citrus fruit (RR 0.85), and cruciferous vegetables (RR 0.84). Finally, three occupations with the highest risk were tobacco workers (RR 1.72), dye workers (RR 1.58), and chimney sweeps (RR 1.53). The probability of causation for individual factors ranged from 4 to 68 %. The combined probability of causation was 81.8 %. Modification of lifestyle and occupational exposures can considerably reduce the bladder cancer burden. While smoking remains one of the key risk factors, also several diet-related and occupational factors are very relevant.

The incidence of breast cancer among female flight attendants: an updated meta-analysis

BACKGROUND

Several studies have indicated an increased risk of breast cancer (BC) among female flight attendants (FFAs); however, the results from epidemiological studies were not consistent. We thus conducted an updated meta-analysis to re-assess the risk of BC among FFAs, according to the MOOSE guideline.

METHODS

A systematical search of PubMed and Embase for relevant observational studies up to March 2016 was performed, supplemented by manual reviews of bibliographies in relevant studies. A random effect model was conducted to calculate the combined standard incidence ratio (SIR) and 95% confidence interval (95% CI) in BC risk.

RESULTS

Of the 719 citations retrieved, 10 were included, with more than 31 679 participants and 821 new cases. The combined SIR (95% CI) for BC in FFAs was 1.40 (95%CI 1.30-1.50), with no significant heterogeneity (P = 0.744; I(2 )=( )0.0%) or publication bias (Begg's test: z = 0.72, P = 0.474; Egger's test: t = 0.25, P = 0.805) among the included studies. The results were not significantly modified by publication year, geographic area, study quality or whether the fertility variables were adjusted.

CONCLUSIONS

Our meta-analysis suggests that FFAs have a higher risk of BC compared with the general population. More vigorous studies with larger sample sizes based on other populations, including the Chinese, are needed.

Cosmic radiation and cancer: is there a link?

Cosmic radiation can cause genetic and cytogenetic damage. Certain occupations including airline pilots and cabin crew are acknowledged to have a greater exposure to cosmic radiation. In a systematic search of MEDLINE, performed from 1990 to 2014, we analyzed clinical studies using the keywords: cosmic radiation, cancer, chromosome aberration, pilots and astronauts. Increased incidence of skin cancers among airline cabin crew has been reported in a number of studies and appears to be the most consistent finding. However, as with other cancers, it is unclear whether increased exposure to cosmic radiation is a factor in the increased incidence or whether this can be explained by lifestyle factors. Further research is needed to clarify the risk of cancer in relation to cosmic radiation.

Trabalho e saúde dos comissários de bordo: uma revisão

Resumo Introdução: com o aumento do número de voos e passageiros, as tarefas atribuídas aos comissários de bordo tornam-se mais complexas, podendo gerar sobrecarga e prejuízo à saúde e ao desempenho desses trabalhadores. Objetivos: identificar e sistematizar os artigos publicados em periódicos científicos, sobre o impacto de fatores físicos, ambientais e organizacionais do trabalho dos comissários de bordo na saúde desses trabalhadores. Método: revisão sistemática da literatura, em português e inglês, utilizando as palavras-chave "aeronave", "cabine", "transporte aéreo", "comissário de bordo" e "trabalho", nas bases de dados ScienceDirect, PubMed, Scopus, ProQuest e SciELO, considerando o período de 1983 a 2013. Resultados: 65 artigos atenderam aos critérios de inclusão. Verificou-se um predomínio de trabalhos com foco em fatores físicos e/ou relacionados à saúde/doença e em fatores relacionados à satisfação no trabalho e poucos estudos abordando a organização do trabalho. Conclusão: os estudos encontrados analisaram os fatores presentes nas situações de trabalho de comissários de bordo de forma isolada. Não foram encontrados estudos que adotassem uma metodologia de análise das situações de trabalho que possibilitasse estabelecer inter-relações entre os fatores determinantes da carga de trabalho desses trabalhadores e os impactos para sua saúde.

Breast Imaging in the Era of Big Data: Structured Reporting and Data Mining

OBJECTIVE

The purpose of this article is to describe structured reporting and the development of large databases for use in data mining in breast imaging.

CONCLUSION

The results of millions of breast imaging examinations are reported with structured tools based on the BI-RADS lexicon. Much of these data are stored in accessible media. Robust computing power creates great opportunity for data scientists and breast imagers to collaborate to improve breast cancer detection and optimize screening algorithms. Data mining can create knowledge, but the questions asked and their complexity require extremely powerful and agile databases. New data technologies can facilitate outcomes research and precision medicine.

Modeling flight attendants' exposure to secondhand smoke in commercial aircraft: historical trends from 1955 to 1989

Flight attendants were exposed to elevated levels of secondhand smoke (SHS) in commercial aircraft when smoking was allowed on planes. During flight attendants' working years, their occupational SHS exposure was influenced by various factors, including the prevalence of active smokers on planes, fliers' smoking behaviors, airplane flight load factors, and ventilation systems. These factors have likely changed over the past six decades and would affect SHS concentrations in commercial aircraft. However, changes in flight attendants' exposure to SHS have not been examined in the literature. This study estimates the magnitude of the changes and the historic trends of flight attendants' SHS exposure in U.S. domestic commercial aircraft by integrating historical changes of contributing factors. Mass balance models were developed and evaluated to estimate flight attendants' exposure to SHS in passenger cabins, as indicated by two commonly used tracers (airborne nicotine and particulate matter (PM)). Monte Carlo simulations integrating historical trends and distributions of influence factors were used to simulate 10,000 flight attendants' exposure to SHS on commercial flights from 1955 to 1989. These models indicate that annual mean SHS PM concentrations to which flight attendants were exposed in passenger cabins steadily decreased from approximately 265 μg/m(3) in 1955 and 1960 to 93 μg/m(3) by 1989, and airborne nicotine exposure among flight attendants also decreased from 11.1 μg/m(3) in 1955 to 6.5 μg/m(3) in 1989. Using duration of employment as an indicator of flight attendants' cumulative occupational exposure to SHS in epidemiological studies would inaccurately assess their lifetime exposures and thus bias the relationship between the exposure and health effects. This historical trend should be considered in future epidemiological studies.

Prevalence of risk factors for breast cancer in German airline cabin crew: a cross-sectional study

BACKGROUND

Many epidemiological studies point to an increased risk of breast cancer among female airline cabin crew. Possible causes include occupational factors (e.g. cosmic radiation exposure, chronodisruption), as well as lifestyle and reproductive factors.

AIMS

To investigate the frequency of various risk factors in German flight attendants which are recognised to be associated with breast cancer.

METHODS

2708 current and former female cabin crew were randomly selected by a flight attendants' union and mailed a questionnaire; 1311 responded (48% response). Descriptive statistics were used to compare the distribution of breast cancer risk factors with general German population data.

RESULTS

On average, cabin crew were 3.0 cm (95% CI 2.7-3.3) taller than the comparison group, while their body mass index was 2.5 kg/m(2) (95% CI 2.4-2.6) lower. We found less use of hormone replacement therapy, but longer average use of oral contraceptives. Nulliparity among respondents aged 45+ was 57% (95% CI 54%-60%) compared to 16%. Average age at first birth was 32.1 years (95% CI 31.7-32.4) vs. 25.5 years. The birth rate was 0.62 (95% CI 0.58-0.67), less than half the population average of 1.34. Alcohol consumption was considerably higher, whereas cabin crew tended to smoke less and performed more physical exercise.

CONCLUSION

We found important differences in terms of anthropometric, gynaecological, reproductive and lifestyle factors. Some of these differences (e.g. higher nulliparity, alcohol consumption, taller size) could contribute to a higher breast cancer risk, whereas others could lead to a reduction (e.g. increased physical exercise, lower BMI, less HRT use).

The self-reported health of U.S. flight attendants compared to the general population

BACKGROUND

Few studies have examined the broad health effects of occupational exposures in flight attendants apart from disease-specific morbidity and mortality studies. We describe the health status of flight attendants and compare it to the U.S. population. In addition, we explore whether the prevalence of major health conditions in flight attendants is associated with length of exposure to the aircraft environment using job tenure as a proxy.

METHODS

We surveyed flight attendants from two domestic U.S. airlines in 2007 and compared the prevalence of their health conditions to contemporaneous cohorts in the National Health and Nutrition Survey (NHANES), 2005-2006 and 2007-2008. We weighted the prevalence of flight attendant conditions to match the age distribution in the NHANES and compared the two populations stratified by gender using the Standardized Prevalence Ratio (SPR). For leading health conditions in flight attendants, we analyzed the association between job tenure and health outcomes in logistic regression models.

RESULTS

Compared to the NHANES population (n =5,713), flight attendants (n = 4,011) had about a 3-fold increase in the age-adjusted prevalence of chronic bronchitis despite considerably lower levels of smoking. In addition, the prevalence of cardiac disease in female flight attendants was 3.5 times greater than the general population while their prevalence of hypertension and being overweight was significantly lower. Flight attendants reported 2 to 5.7 times more sleep disorders, depression, and fatigue, than the general population. Female flight attendants reported 34% more reproductive cancers. Health conditions that increased with longer job tenure as a flight attendant were chronic bronchitis, heart disease in females, skin cancer, hearing loss, depression and anxiety, even after adjusting for age, gender, body mass index (BMI), education, and smoking.

CONCLUSIONS

This study found higher rates of specific diseases in flight attendants than the general population. Longer tenure appears to explain some of the higher disease prevalence. Conclusions are limited by the cross-sectional design and recall bias. Further study is needed to determine the source of risk and to elucidate specific exposure-disease relationships over time.

Shift work and cancer risk: potential mechanistic roles of circadian disruption, light at night, and sleep deprivation

Shift work that includes a nighttime rotation has become an unavoidable attribute of today's 24-h society. The related disruption of the human circadian time organization leads in the short-term to an array of jet-lag-like symptoms, and in the long-run it may contribute to weight gain/obesity, metabolic syndrome/type II diabetes, and cardiovascular disease. Epidemiologic studies also suggest increased cancer risk, especially for breast cancer, in night and rotating female shift workers. If confirmed in more controlled and detailed studies, the carcinogenic effect of night and shift work will constitute additional serious medical, economic, and social problems for a substantial proportion of the working population. Here, we examine the possible multiple and interconnected cancer-promoting mechanisms as a consequence of shift work, i.e., repeated disruption of the circadian system, pineal hormone melatonin suppression by exposure to light at night, sleep-deprivation-caused impairment of the immune system, plus metabolic changes favoring obesity and generation of proinflammatory reactive oxygen species.

Radiotherapy as a risk factor for malignant melanoma after childhood skin hemangioma

The aim of this study was to determine therapy-related risk factors for the development of melanoma after hemangioma. A cohort study was conducted among 4620 patients treated before 16 years of age for skin hemangioma in France. A nested case-control study was also conducted on 13 patients who developed a melanoma (cases) matched with five controls in cohort according to sex, age at the hemangioma diagnostic, the calendar year of occurrence of the hemangioma, and follow-up. The radiation dose received at the site of the melanoma and at the same site in controls was estimated, and named 'local dose'. A total of 13 melanomas were registered during an average follow-up of overall 35 years, the risk of developing melanoma after a hemangioma treatment was 2.5-fold higher [95% confidence interval (CI): 1.4-4.1] compared with that of the general population, this ratio being only 0.8 (95% CI: 0.05-3.6) in 896 patients who did not receive radiotherapy, but 3.0 (95% CI: 1.6-5.1) after radiotherapy. When adjusting on sex, age, and year of the treatment and follow-up duration, melanoma risk was 11.9 (95% CI: 1.4-123) times higher in patients treated with ytrium 90 than in the ones who did not received radiotherapy. In the case-control study, the risk of melanoma was not linked to the local radiation dose. Indeed, the increase in melanoma risk was observed even for very low local doses. Compared with the corresponding skin areas in patients who did not receive radiotherapy, the ones having received less than 0.001 Gy had a melanoma risk of 3.9 (95% CI: 0.5-32) and those who received more than 0.01 Gy had a risk of 6.9 (0.5-99). This study suggests that radiation therapy of skin hemangioma increases the risk of further melanoma, but we were not able to evidence a relation with the local dose. Nevertheless, childhood treated for hemangioma should be considered at risk for developing melanoma and suspicious pigmented lesions should be carefully evaluated even far from treated areas.

Gamma-ray-induced mutagen sensitivity and risk of sporadic breast cancer in young women: a case-control study

Hypersensitivity to radiation exposure has been suggested to be a risk factor for the development of breast cancer. In this case-control study of 515 young women (≤ 55 years) with newly diagnosed sporadic breast cancer and 402 cancer-free controls, we examined the radiosensitivity as measured by the frequency of chromatid breaks induced by gamma-radiation exposure in the G2 phase of phytohemagglutinin-stimulated and short-term cultured fresh lymphocytes. We found that the average chromatid breaks per cell from 50 well-spread metaphases were statistically significantly higher in 403 non-Hispanic White breast cancer patients (0.52 ± 0.22) than that in 281 non-Hispanic White controls (0.44 ± 0.16) (P value < 0.001), and in 60 Mexican American breast cancer patients (0.52 ± 0.19) than that in 65 Mexican American controls (0.44 ± 0.16) (P value = 0.021), but the difference was not significant in African Americans (52 cases [0.45 ± 0.16] versus 56 controls [0.47 ± 0.16], P = 0.651). The frequency of chromatid breaks per cell above the median of control subjects was associated with two-fold increased risk for breast cancer in non-Hispanic Whites and Mexican Americans. A dose-response relationship was evident between radiosensitivity and risk for breast cancer (P (trend) < 0.001) in these two ethnic groups. We concluded that gamma-ray-induced mutagen sensitivity may play a role in susceptibility to breast cancer in young non-Hispanic White and Mexican American women.

Cause-specific mortality among a cohort of U.S. flight attendants

BACKGROUND

We evaluated mortality among 11,311 former U.S. flight attendants. The primary a priori outcomes of interest were breast cancer and melanoma.

METHODS

Vital status was ascertained through 2007, and life table analyses was conducted. Cumulative exposure to cosmic radiation and circadian rhythm disruption were estimated from work history data and historical published flight schedules.

RESULTS

All-cause mortality was less than expected among women but was elevated among men, primarily due to elevated HIV-related disease mortality. Mortality from breast cancer among women and melanoma was neither significantly elevated nor related to metrics of exposure. Mortality was elevated for non-Hodgkin's lymphoma among men; for alcoholism, drowning, and intentional self-harm among women; and for railway, water, and air transportation accidents.

CONCLUSIONS

We found no evidence of increased breast cancer or melanoma mortality. Limitations include reliance on mortality data and limited power resulting from few melanoma deaths and relatively short employment durations.

'Lifestyle' and cancer rates in former East and West Germany: the possible contribution of diagnostic radiation exposures

Breast and prostatic cancer as well as leukaemia in childhood have remarkably increased over some decades in the Federal Republic of Germany as well as in several other highly developed industrial nations. Such increase was much less or not observable in East Germany between 1960 and 1989 where diagnostic exposures were applied to a lesser extent. Low-level radiation can cause these diseases and the difference of cancer rates gives rise to renewed evaluation of current risk estimates. Risk factors for radiation-induced childhood leukaemia and breast cancer are derived from the literature, considering a higher relative biological effectiveness of diagnostic X rays in comparison to the A-bomb gamma rays in Hiroshima and Nagasaki. The prostate is not considered as radiation sensitive by the ICRP. But following a variety of low-level findings in the last two decades it was shown by Myles et al. in the UK that prostatic cancer is inducible by diagnostic X-ray procedures. From their study in men below the age of 60, a doubling dose of about 20 mSv can be estimated. Medical exposures of the considered tissues are taken from published data for East and West Germany. The difference in breast cancer mortality can be explained by diagnostic exposures. The contribution of these to prostatic cancer and childhood leukaemia must be regarded as relevant in current incidences. Reduction of diagnostic exposures would be an important measure for preventing several prominent cancer diseases.

Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans

CONTEXT

Millions of individuals habitually expose themselves to room light in the hours before bedtime, yet the effects of this behavior on melatonin signaling are not well recognized.

OBJECTIVE

We tested the hypothesis that exposure to room light in the late evening suppresses the onset of melatonin synthesis and shortens the duration of melatonin production.

DESIGN

In a retrospective analysis, we compared daily melatonin profiles in individuals living in room light (<200 lux) vs. dim light (<3 lux).

PATIENTS

Healthy volunteers (n = 116, 18-30 yr) were recruited from the general population to participate in one of two studies.

SETTING

Participants lived in a General Clinical Research Center for at least five consecutive days.

INTERVENTION

Individuals were exposed to room light or dim light in the 8 h preceding bedtime.

OUTCOME MEASURES

Melatonin duration, onset and offset, suppression, and phase angle of entrainment were determined.

RESULTS

Compared with dim light, exposure to room light before bedtime suppressed melatonin, resulting in a later melatonin onset in 99.0% of individuals and shortening melatonin duration by about 90 min. Also, exposure to room light during the usual hours of sleep suppressed melatonin by greater than 50% in most (85%) trials.

CONCLUSIONS

These findings indicate that room light exerts a profound suppressive effect on melatonin levels and shortens the body's internal representation of night duration. Hence, chronically exposing oneself to electrical lighting in the late evening disrupts melatonin signaling and could therefore potentially impact sleep, thermoregulation, blood pressure, and glucose homeostasis.

Cancer mortality among German aircrew: second follow-up

Aircrew members are exposed to cosmic radiation and other specific occupational factors. In a previous analysis of a large cohort of German aircrew, no increase in cancer mortality or dose-related effects was observed. In the present study, the follow-up of this cohort of 6,017 cockpit and 20,757 cabin crew members was extended by 6 years to 2003. Among male cockpit crew, the resulting all-cancer standardized mortality ratio (SMR) (n = 127) is 0.6 (95% CI 0.5-0.8), while for brain tumors it is 2.1 (95% CI 1.0-3.9). The cancer risk is significantly raised (RR = 2.2, 95% CI 1.2-4.1) among cockpit crew members employed 30 years or more compared to those employed less than 10 years. Among both female and male cabin crew, the all-cancer SMR and that for most individual cancers are close to 1. The SMR for breast cancer among female crew is 1.2 (95% CI 0.8-1.8). Non-Hodgkin's Lymphoma among male cabin crew is increased (SMR 4.2; 95% CI 1.3-10.8). However, cancers associated with radiation exposure are not raised in the cohort. It is concluded that among cockpit crew cancer mortality is low, particularly for lung cancer. The positive trend of all cancer with duration of employment persists. The increased brain cancer SMR among cockpit crew requires replication in other cohorts. For cabin crew, cancer mortality is generally close to population rates. Cosmic radiation dose estimates will allow more detailed assessments, as will a pooling of updated aircrew studies currently in planning.

Epidemiological studies of cancer in aircrew

Exposure to cosmic ionising radiation, in addition to other specific occupational risks, is of concern to aircrew members. Epidemiological studies provide an objective way to assess the health of this occupational group. We systematically reviewed the epidemiological literature on health of aircrew members since 1990, focusing on cancer as the endpoint of interest. Sixty-five relevant publications were identified and reviewed. Whereas overall cancer incidence and mortality was generally lower than in the comparison population, consistently elevated risks were reported for breast cancer incidence in female aircrew members and for melanoma in both male and female aircrew members. Brain cancer was increased in some studies among pilots. Occasionally trends of increasing cancer mortality or incidence with increasing estimated radiation dose were reported. Ionising radiation is considered to contribute little if at all to the elevated risks for cancers among aircrew, whereas excess ultraviolet radiation is a probable cause of the increased melanoma risk.

Light-at-night, circadian disruption and breast cancer: assessment of existing evidence

BACKGROUND

Breast cancer incidence is increasing globally for largely unknown reasons. The possibility that a portion of the breast cancer burden might be explained by the introduction and increasing use of electricity to light the night was suggested >20 years ago.

METHODS

The theory is based on nocturnal light-induced disruption of circadian rhythms, notably reduction of melatonin synthesis. It has formed the basis for a series of predictions including that non-day shift work would increase risk, blind women would be at lower risk, long sleep duration would lower risk and community nighttime light level would co-distribute with breast cancer incidence on the population level.

RESULTS

Accumulation of epidemiological evidence has accelerated in recent years, reflected in an International Agency for Research on Cancer (IARC) classification of shift work as a probable human carcinogen (2A). There is also a strong rodent model in support of the light-at-night (LAN) idea.

CONCLUSION

If a consensus eventually emerges that LAN does increase risk, then the mechanisms for the effect are important to elucidate for intervention and mitigation. The basic understanding of phototransduction for the circadian system, and of the molecular genetics of circadian rhythm generation are both advancing rapidly, and will provide for the development of lighting technologies at home and at work that minimize circadian disruption, while maintaining visual efficiency and aesthetics. In the interim, there are strategies now available to reduce the potential for circadian disruption, which include extending the daily dark period, appreciate nocturnal awakening in the dark, using dim red light for nighttime necessities, and unless recommended by a physician, not taking melatonin tablets.

Health physics and aviation: solar cycle 23 (1996-2008)

We continue our description of the scientific and professional activities that were initiated by the classification of airline flight crewmembers as occupational radiation workers in 1994, specifically looking at the period between 1996 and 2008. During this period, radiation measurement programs were conducted on numerous commercial aircraft flights. Epidemiological studies have looked at the incidence of cancer in pilots and flight attendants, with mixed conclusions. The Federal Aviation Administration (FAA) released revised versions of its CARI software, the computer program designed to evaluate radiation exposures received on user-defined flight plans. Additional dose-evaluation programs have been made available by other entities. In May 2000, member states of the European Union (EU) adopted regulations that apply to the air carriers in all twenty-seven nations requiring education on health risks of in-flight radiation as well as dose assessment for all EU flight crewmembers. The National Oceanic and Atmospheric Administration (NOAA) revised its classification scheme for space weather events including radiation-producing solar storms. In 2005, the FAA created a Solar Particle Alert system to warn aircraft of high radiation levels caused by significant events of this type. There is now an early-warning system for potentially harmful solar particle events. This new system depends on the earlier arrival time of relativistic electrons compared with the heavier particulate radiation.

Breast cancer incidence following low-dose rate environmental exposure: Techa River Cohort, 1956-2004

In the 1950s, the Mayak nuclear weapons facility in Russia discharged liquid radioactive wastes into the Techa River causing exposure of riverside residents to protracted low-to-moderate doses of radiation. Almost 10,000 women received estimated doses to the stomach of up to 0.47 Gray (Gy) (mean dose=0.04 Gy) from external gamma-exposure and (137)Cs incorporation. We have been following this population for cancer incidence and mortality and as in the general Russian population, we found a significant temporal trend of breast cancer incidence. A significant linear radiation dose-response relationship was observed (P=0.01) with an estimated excess relative risk per Gray (ERR/Gy) of 5.00 (95% confidence interval (CI), 0.80, 12.76). We estimated that approximately 12% of the 109 observed cases could be attributed to radiation.