Breast cancer risk among Finnish cabin attendants: a nested case-control study

Background: Earlier studies have found increased breast cancer risk among female cabin crew. This has been suggested to reflect lifestyle factors (for example, age at first birth), other confounding factors (for example, age at menarche), or occupational factors such as exposure to cosmic radiation and circadian rhythm alterations due to repeated jet lag.     

Cancer incidence among Norwegian airline cabin attendants

BACKGROUND: Cabin crews are exposed to cosmic radiation at work and this may increase their incidence of radiation-induced cancers. Former studies indicate an increased risk of breast cancer. METHODS: A retrospective cohort study was performed. The cohort was established from the files of the Civil Aviation Administration and included people with a valid licence as a cabin attendant between 1950 and 1994. The cohort was linked to the Cancer Registry of Norway. Observed number of cases was compared with expected, based on national rates. Breast cancer incidence was analysed, adjusting for individual fertility variables. RESULTS: A group of 3693 cabin attendants were followed over 72 804 person-years. Among the women, 38 cases of breast cancer were observed (standardized incidence ratio (SIR) = 1.1, 95% CI : 0.8-1.5). Among men excess risks were found for cancers in the upper respiratory and gastric tract (SIR = 6.0, 95% CI : 2.7-11.4) and cancer of the liver (two cases, SIR = 10.8, 95% CI : 1.3-39.2). For both sexes elevated risks were found for malignant melanoma and non-melanoma skin cancer; for men these were SIR = 2.9 (95% CI : 1.1-6.4) and SIR = 9.9 (95% CI : 4.5-18.8) respectively, while for women these were SIR = 1.7 (95% CI : 1.0-2.7) and SIR = 2.9 (95% CI : 1.0-6.9) respectively. For no cancer site was a significant decreased risk found. CONCLUSIONS: An increased risk of radiation-induced cancers was not observed. The excess risks of some other cancers are more probably explained by factors related to lifestyle.     

Mortality from cancer and other causes among airline cabin attendants in Europe: a collaborative cohort study in eight countries

There is concern about the health effects of exposure to cosmic radiation during air travel. To study the potential health effects of this and occupational exposures, the authors investigated mortality patterns among more than 44,000 airline cabin crew members in Europe. A cohort study was performed in eight European countries, yielding approximately 655,000 person-years of follow-up. Observed numbers of deaths were compared with expected numbers based on national mortality rates. Among female cabin crew, overall mortality (standardized mortality ratio (SMR) = 0.80, 95% confidence interval (CI): 0.73, 0.88) and all-cancer mortality (SMR = 0.78, 95% CI: 0.66, 0.95) were slightly reduced, while breast cancer mortality was slightly but nonsignificantly increased (SMR = 1.11, 95% CI: 0.82, 1.48). In contrast, overall mortality (SMR = 1.09, 95% CI: 1.00, 1.18) and mortality from skin cancer (for malignant melanoma, SMR = 1.93, 95% CI: 0.70, 4.44) among male cabin crew were somewhat increased. The authors noted excess mortality from aircraft accidents and from acquired immunodeficiency syndrome in males. Among airline cabin crew in Europe, there was no increase in mortality that could be attributed to cosmic radiation or other occupational exposures to any substantial extent. The risk of skin cancer among male crew members requires further attention.     

Pregnancy outcome among offspring of airline pilots and cabin attendants

OBJECTIVES: This study assessed the occurrence of perinatal death, low birthweight, preterm birth, and birth defects (total, major, neural tube defects, total cleft, cleft palate, hypospadias, and Down syndrome) in the offspring of airline pilots and cabin attendants. METHODS: A cohort of offspring of airline pilots and cabin attendants was established and characterized in terms of parental exposure to cosmic radiation the year before birth or ever. Pregnancy outcome was derived from the Medical Birth Register of Norway. The reference group comprised offspring of parents without occupational exposure to cosmic radiation. RESULTS: No deviant risks were observed for the offspring of male pilots, either for the year preceding birth (N=2,111) or ever (N=2,356). Specific birth outcomes were fewer for the pilots than for the referents (N=1,621,186), except for Down syndrome, which was more frequent [odds ratio (OR) 1.41, 95% confidence interval (95% CI) 0.53-3.76]. For exposure the year preceding birth (N=2,512), the risk of low birthweight was lower for the female cabin attendants than for the referents (adjusted OR 0.83, 95% CI 0.69-1.00), while Down syndrome was more frequent (OR 1.44, 95% CI 0.60-3.47). For exposure ever (N=3346), the risk of low birthweight was lower (OR 0.82, 95% CI 0.70-0.96) for the cabin attendants, while hypospadias (OR 1.18, 95% CI 0.61-3.04) and Down syndrome (OR 1.79, 95% CI 0.03-3.45) were more frequent CONCLUSIONS: In general, offspring of air pilots and cabin attendants do not seem to be at increased risk of adverse pregnancy outcome.     

Plasma enterolignan concentrations and colorectal cancer risk in a nested case-control study

Enterolignans are biphenolic compounds that possess several biologic activities whereby they may influence carcinogenesis. The authors investigated the association between plasma enterolactone and enterodiol and colorectal cancer risk in a Dutch prospective study. Among more than 35,000 participants aged 20-59 years, 160 colorectal cancer cases were diagnosed after 7.5 years of follow-up (1987-2003). Cohort members who were frequency-matched to the cases on age, sex, and study center were selected as controls (n = 387). Plasma enterodiol and enterolactone were not associated with risk of colorectal cancer after adjustment for known colorectal cancer risk factors (highest quartile vs. lowest: for enterodiol, odds ratio = 1.11, 95% confidence interval: 0.56, 2.20 (p-trend = 0.75); for enterolactone, odds ratio = 1.70, 95% confidence interval: 0.88, 3.27 (p-trend = 0.15)). However, sex (p-interaction = 0.06) and body mass index (p-interaction < 0.01) modified the relation between plasma enterolactone and colorectal cancer risk; increased risks were observed among women and subjects with a high body mass index. The association between plasma enterodiol and colorectal cancer risk was modified by smoking status; risk was increased among current smokers (p-interaction < 0.01). These findings do not support the hypothesis that high plasma enterodiol or enterolactone concentrations are associated with reduced risk of colorectal cancer.     

Mortality from cancer and other causes among airline cabin attendants in Germany, 1960-1997

Airline cabin attendants are exposed to several potential occupational hazards, including cosmic radiation. Little is known about the mortality pattern and cancer risk of these persons. The authors conducted a historical cohort study among cabin attendants who had been employed by two German airlines in 1953 or later. Mortality follow-up was completed through December 31, 1997. The authors computed standardized mortality ratios (SMRs) for specific causes of death using German population rates. The effect of duration of employment was evaluated with Poisson regression. The cohort included 16,014 women and 4,537 men (approximately 250,000 person-years of follow-up). Among women, the total number of deaths (n = 141) was lower than expected (SMR = 0.79, 95% confidence interval (CI): 0.67, 0.94). The SMR for all cancers (n = 44) was 0.79 (95% CI: 0.54, 1.17), and the SMR for breast cancer (n = 19) was 1.28 (95% CI: 0.72, 2.20). The SMR did not increase with duration of employment. Among men, 170 deaths were observed (SMR = 1.10, 95% CI: 0.94, 1.28). The SMR for all cancers (n = 21) was 0.71 (95% CI: 0.41, 1.18). The authors found a high number of deaths from acquired immunodeficiency syndrome (SMR = 40; 95% CI: 28.9, 55.8) and from aircraft accidents among the men. In this cohort, ionizing radiation probably contributed less to the small excess in breast cancer mortality than reproductive risk factors. Occupational causes seem not to contribute strongly to the mortality of airline cabin attendants.     

Benzodiazepine use and risk of dementia: a nested case-control study

The objective of this article was to examine the possible association between benzodiazepine use and the risk of dementia in the elderly. This was a nested case--control study set in community settings in Bordeaux area, France. The participants were a representative sample of 3,777 elderly persons (65 years of age and older) followed from 1989 to 1997. The main outcome measures were the use of benzodiazepines in incident cases of dementia versus nondemented controls. On the basis of medical and psychological data, 150 patients were diagnosed with dementia according to the criteria of the third revision of the Diagnostic and Statistical Manual of Mental Disorders. Information on benzodiazepine use was obtained by face-to-face interview and visual assessment of patient's medicine chest by a trained neuropsychologist. After controlling for age, gender, education level, living alone, wine consumption, psychiatric history, and depressive symptomatology, ever use of benzodiazepines was associated with a significantly increased risk of dementia [adjusted odds ratio (OR), 1.7; 95% confidence interval, 1.2-2.4]. Former use was associated with a significantly increased risk of dementia (adjusted OR, 2.3; 95% CI,1.2-4.5). No association was found between dementia and the current use of benzodiazepines (adjusted OR, 1.0; 95% CI, 0.6-1.6). Our finding suggest that former use of benzodiazepines could be a risk factor for dementia, but more detailed investigation are needed.     

Breast cancer risk associated with different HRT formulations: a register-based case-control study

Background  

Previous epidemiological studies have inconsistently shown a modestly increased breast cancer risk associated with hormone replacement therapy (HRT). Limited information is available about different formulations - particularly concerning different progestins.     

Carpal tunnel syndrome: a nested case-control study of risk factors in women

Risk factors for the development of carpal tunnel syndrome in women were studied by means of a nested case-control analysis of a prospective cohort study of the health effects of oral contraception in British women. A total of 1,264 women who had a diagnosis of carpal tunnel syndrome reported by their general practitioner between 1968 and 1993 were compared with 1,264 age-matched control women who did not have this diagnosis. The syndrome was associated in older women with some hormonal factors, notably past use of oral contraception (adjusted odds ratio in women aged 40 years and over = 1.38, 95 percent confidence interval: 1.08, 1.76) and more generally with obesity (adjusted odds ratio = 1.68, 95 percent confidence interval: 1.29, 2.18). However, the strongest link was with a previous history of another musculoskeletal complaint for which consultation had been sought (adjusted odds ratio = 1.98, 95 percent confidence interval: 1.61, 2.42). Previous findings of a higher risk in women with diabetes and myxoedema were confirmed, but these contribute only a small proportion of all cases in women. There was no link with psychologic problems or nonmusculoskeletal pain complaints. The previously described increased incidence of carpal tunnel syndrome in women may be partly due to hormonal factors, but is also related to an underlying propensity to musculoskeletal problems and their higher overall frequency in women.     

A retrospective cohort mortality study of Italian commercial airline cockpit crew and cabin attendants, 1965-96

A retrospective cohort mortality study was conducted among Italian commercial flight personnel for the period 1965-1996. The cohort was composed of 3,022 male cockpit crew members and 3,418 male and 3,428 female cabin attendants. Cause-specific standardized mortality ratios (SMRs) and exact 95% confidence intervals (CIs) were calculated as estimates of the relative risk. Mortality from all cancers was less than expected for all categories (SMRs of 0.58 for male cockpit crew, 0.67 for male cabin attendants, and 0.90 for female cabin attendants). Among male flight personnel, the SMR for leukemia was somewhat elevated (SMR 1.73; 95% CI: 0.75-3.41) based on eight deaths, with a positive trend by length of employment (p = 0.046). Additionally, an excess of death by suicide was seen among female cabin attendants (SMR 3.38; 95% CI: 1.24-7.35). Other Italian studies of flight personnel are under way, including a detailed assessment of cosmic radiation exposure and investigations of non-radiation occupational risk factors and prevalence of nonfatal outcomes.     

Oesophageal cancer and occupational exposure to rubber: a nested case-control study

Findings for cancer of the oesophagus in the rubber industry are not consistent between studies, and derive from too few studies. Few studies were carried out to examine risks of oesophageal cancer in different departments and the confounding by non-occupational risk factors such as smoking, drinking, and economic status. In this paper these questions have been explored. Following a nested case-control study, the data were used of nine oesophageal cancer deaths during 1973-1995 and 36 controls matched for sex and age from the same cohort of a rubber plant workers. Oesophageal cancer risks for exposure to rubber were assessed, unadjusted and adjusted for non-occupational factors by conditional logistic regression. In grouped analysis, odds ratios (ORs) for oesophageal cancer were found to be 2.67 (95%CI=0.42,17.0) for milling, etc. workers and 1. 40 (95%CI=0.24,7.97) for building workers, who worked for one or more years. No excess risks were found in the remaining three departments. The models for continuous exposure variables indicated that a one-unit year change in the milling, etc. department was associated with a 4% increment in the OR. When adjusted for serum cholesterol level, the 6% increase (OR) was observed. Significant associations between risk for oesophageal cancer and specific exposures or processes within the rubber plant were not found. The slight excess risk for oesophageal cancer in the rubber plant may be related to exposure to dusts and solvents.     

静态行为与心脑血管病死亡关系巢式病例对照研究

目的 了解静态行为与心脑血管病死亡的关系。方法 于2010年10月-2014年12月应用巢式病例对照研究方法对江苏省8 275名≥18周岁未患心脑血管病的常住居民作为研究队列进行随访,以队列中96例新发心脑血管病死亡患者作为病例组,并按照成组设计、病例与对照1：5的原则从随访队列中未发生心脑血管病事件人群中抽取480人作为对照组,应用多因素logistic回归分析方法,在调整可能的混杂因素后分析静态行为与心脑血管病死亡间的关系。结果 在调整年龄、文化程度、家庭平均年收入、吸烟、饮酒和血压等因素后,每日静态行为时间≥6 h者心脑血管病死亡风险为每日静态行为时间<2 h者的5.94倍（95%CI=2.01~17.60）;静态行为与吸烟行为在心脑血管病死亡上存在交互作用（OR_交互=1.37,95%CI=1.01~3.56）,现在吸烟同时每日静态行为时间≥6 h者心脑血管病死亡风险为从不吸烟且每日静态行为时间<2 h者的2.46倍（95%CI=1.03~5.88）,未发现静态行为与饮酒行为在心脑血管病死亡上存在交互作用（OR_交互=0.91,95%CI=0.78~1.06）。结论 每日静态行为时间过长可以单独或通过与吸烟行为相互作用而增加心脑血管病的死亡风险。     

Shift work and the risk of metabolic syndrome: a nested case-control study

The aim of the present study was to examine the association between shift work and the metabolic syndrome (MetS) using a large-scale longitudinal study design. Data were collected from a historical cohort of health checkups in the Japanese population. The baseline survey, which involved 16,952 inhabitants of the Minami Saku area of the Nagano Prefecture, was started in 1978. A nested case-control study was conducted between 1987 and 1990. This analysis was restricted to 6,712 men and women (age range 25-59 years). A conditional logistic regression model was used to estimate the risk of MetS associated with shift work. Compared with the day workers, shift workers had a significantly higher risk of MetS (odds ratio 1.87; 95% CI, 1.13-3.08). Our results demonstrate that shift work was strongly associated with MetS. The study suggests appropriate dietary habits as a basis for managing the MetS risk of shift workers.     

Breast cancer risk and oral contraceptive use: results from a large case-control study.

The association between oral contraceptive use and breast cancer risk was examined using data from a case-control study of breast cancer in Long Island, New York. Cases were defined as female residents of Nassau and Suffolk Counties between the ages of 20 and 79, diagnosed with breast cancer between January 1, 1984 and December 31, 1986. Age- and county-matched controls were selected from driver's license files. Among all women under age 70 at diagnosis, there was no association between oral contraceptive use and breast cancer; there was, however, a positive association in the subgroup ages 20-49 (adjusted odds ratio = 1.68, 95% CI: 1.16-2.42). Risk increased with increasing duration of use, but did not differ between women who first used oral contraceptives before the first pregnancy and those who first used them later, or between women who first used oral contraceptives before age 25 and those who first used them at a later age. Risk also appeared to increase with number of years of use before the first pregnancy or before age 25, although numbers were small. History of benign breast disease did not influence risk. The association of breast cancer risk with oral contraceptive use appeared stronger in women from Suffolk County than Nassau County.     

Uterine factors and risk of pregnancy in IUD users: a nested case-control study

Scarce data are available on the relation between the effectiveness of intrauterine device (IUD) and the gynecologic features of a woman. A nested case-control study was conducted to determine whether the uterine position and hysterometry affect the pregnancy rate of copper IUD. Seventy-one cases (pregnant women with IUD) and 284 matched controls (1:4) were included. Matching criteria were date of IUD insertion and duration of use. Data were analyzed by conditional logistic regression modeling that considered age, parity and copper surface of IUD as potential confounders. When cases were compared to nonpregnant controls with IUD, the results showed that uterine position and hysterometry were not associated with an increased risk of pregnancy. The findings suggest that the gynecological characteristics of the woman analyzed should not be a criterion for the selection of potential IUD users.     

Herpes simplex virus and risk of cervical cancer: a longitudinal,nested case-control study in the nordic countries

Human papillomaviruses (HPVs) play the major role in cervical carcinogenesis. The authors reevaluated the role of herpes simplex virus type 2 (HSV-2) in this multistage process by conducting a longitudinal, nested case-control study using 1974-1993 data and comparing the results with those from a meta-analysis of studies. A Nordic cohort of 550,000 women was followed up for an average of 5 years, after which 178 cervical carcinoma cases and 527 controls were identified. HSV-2; HPV-16, HPV-18, and HPV-33; and Chlamydia trachomatis antibodies were determined at baseline by HSV-2 glycoprotein gG-2 and HPV virus-like-particle enzyme immunoassays and by using the microimmunofluorescence method. The relative risk of cervical carcinoma was calculated by conditional logistic regression. Longitudinal studies on HSV-2 and cervical neoplasia were identified through MEDLINE (National Library of Medicine, Bethesda, Maryland), and weighted mean relative risks were calculated. Smoking (relative risk = 1.6, 95% confidence interval (CI): 1.1, 2.3) and HPV-16/HPV-18/HPV-33 (relative risk = 2.9, 95% CI: 1.9, 4.3) were both associated with cervical carcinoma. The smoking- and HPV-16/HPV-18/HPV-33-adjusted relative risks for HSV-2 were 1.0 (95% CI: 0.6, 1.7) and 0.7 (95% CI: 0.3, 1.6), respectively, for HPV seropositives. In the meta-analysis, the relative risk for HSV-2 was 0.9 (95% CI: 0.6, 1.3). In both sets of data, HSV-2 did not play a role in cervical carcinogenesis.     

Human chorionic gonadotropin and alpha-fetoprotein concentrations in pregnancy and maternal risk of breast cancer: a nested case-control study

Pregnancy hormones are believed to be involved in the protection against breast cancer conferred by pregnancy. The authors explored the association of maternal breast cancer with human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP). In 2001, a case-control study was nested within the Northern Sweden Maternity Cohort, an ongoing study in which blood samples have been collected from first-trimester pregnant women since 1975. Cases (n = 210) and controls (n = 357) were matched for age, parity, and date of blood donation. Concentrations of hCG and AFP were measured by immunoassay. No overall significant association of breast cancer with either hCG or AFP was observed. However, women with hCG levels in the top tertile tended to be at lower risk of breast cancer than women with hCG levels in the lowest tertile in the whole study population and in subgroups of age at sampling, parity, and age at cancer diagnosis. A borderline-significant decrease in risk with high hCG levels was observed in women who developed breast cancer after the median lag time to cancer diagnosis (> or =14 years; odds ratio = 0.53, 95% confidence interval: 0.27, 1.03; P = 0.06). These findings, though very preliminary, are consistent with a possible long-term protective association of breast cancer risk with elevated levels of circulating hCG in the early stages of pregnancy.