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Surrogate measures of infectious exposures have been consistently associated with lower childhood acute lymphoblastic leukemia (ALL) risk. However, recent reports have suggested that physician-diagnosed early-life infections increase ALL risk, thereby raising the possibility that stronger responses to infections might promote risk. We examined whether medically diagnosed infections were related to childhood ALL risk in an integrated health-care system in the United States. Cases of ALL (n  = 435) diagnosed between 1994–2014 among children aged 0–14 years, along with matched controls (n  = 2,170), were identified at Kaiser Permanente Northern California. Conditional logistic regression was used to estimate risk of ALL associated with history of infections during first year of life and across the lifetime (up to diagnosis). History of infection during first year of life was not associated with ALL risk (odds ratio (OR) = 0.85, 95% confidence interval (CI): 0.60, 1.21). However, infections with at least 1 medication prescribed (i.e. more "severe" infections) were inversely associated with risk (OR = 0.42, 95% CI: 0.20, 0.88). Similar associations were observed when the exposure window was expanded to include medication-prescribed infections throughout the subjects' lifetime (OR = 0.52, 95% CI: 0.32, 0.85). [ABSTRACT FROM AUTHOR]

Linking birth records and cancer registry data from California, we conducted a population-based study with 23,419 cases and 87,593 matched controls born during 1978-2009 to investigate the relationship of parental age to risk of pediatric cancer. Compared with children born to mothers aged 20-24 years, those born to mothers in older age groups had a 13%-36% higher risk of pediatric cancer; the odds ratio for each 5-year increase in maternal age was 1.06 (95% confidence interval (CI): 1.04, 1.09). For cancer diagnosed in children in age groups 0-14 years and 15-19 years, the odds ratios for each 5-year increase in maternal age were 1.05 (95% CI: 1.02, 1.07) and 1.14 (95% CI: 1.09, 1.19), respectively. Having an older father also conferred an increased risk, with an odds ratio for each 5-year increase of 1.03 (95% CI: 1.02, 1.05) for cancer diagnosed at ages 0-19 years and 1.03 (95% CI: 1.02, 1.05) for cancer diagnosed at ages 0-14 years. While advancing maternal age increased risk of leukemia and central nervous system tumors, older paternal age was not associated with risk of either type. Both maternal and paternal older ages were associated with risk of lymphoma. In this large, population-based record-linkage study, advancing parental age, especially advancing maternal age, was associated with higher pediatric cancer risk, with variations across types of cancer. [ABSTRACT FROM AUTHOR]

The relationship of mode of delivery to risk of childhood acute lymphoblastic leukemia (ALL) is uncertain. After linking birth records and cancer registry data from California, we conducted a population-based case-control study to investigate the role of delivery by cesarean section (C-section) in the etiology of childhood ALL. This study included 5,081 cases and 18,927 matched controls born in 1978-2009; more detailed data were available on type of C-section (i.e., elective vs. emergency) for a subset of 1,552 cases and 5,688 controls. No association was observed between C-section overall and childhood ALL risk (<15 years of age), but elective C-section was associated with a significantly elevated risk of ALL (odds ratio (OR) = 1.17, 95% confidence interval (CI): 1.01, 1.36). At the peak ages of ALL incidence (2-4 years), C-section was associated with an 11 % higher risk of ALL (OR = 1.11, 95% CI: 1.01, 1.22) compared with vaginal delivery, and the magnitude of the association was larger for elective C-section (OR = 1.38, 95% CI: 1.11, 1.70). Emergency C-section was not associated with childhood ALL. Because of design features minimizing nonparticipation and inaccurate recall, this record linkage-based study is less prone to bias. Our results suggest that delivery by elective C-section was associated with a higher risk of childhood ALL, especially at the peak ages of incidence. It is important to evaluate possible mechanisms, because this potential risk factor is modifiable. [ABSTRACT FROM AUTHOR]

The association between tobacco smoke and acute myeloid leukemia (AML) is well established in adults but not in children. Individual-level data on parental cigarette smoking were obtained from 12 case-control studies from the Childhood Leukemia International Consortium (CLIC, 1974-2012), including 1,330 AML cases diagnosed at age <15 years and 13,169 controls. We conducted pooled analyses of CLIC studies, as well as meta-analyses of CLIC and non-CLIC studies. Overall, maternal smoking before, during, or after pregnancy was not associated with childhood AML; there was a suggestion, however, that smoking during pregnancy was associated with an increased risk in Hispanics (odds ratio = 2.08, 95% confidence interval (CI): 1.20, 3.61) but not in other ethnic groups. By contrast, the odds ratios for paternal lifetime smoking were 1.34 (95% CI: 1.11, 1.62) and 1.18 (95% CI: 0.92, 1.51) in pooled and meta-analyses, respectively. Overall, increased risks from 1.2- to 1.3-fold were observed for pre- and postnatal smoking (P < 0.05), with higher risks reported for heavy smokers. Associations with paternal smoking varied by histological type. Our analyses suggest an association between paternal smoking and childhood AML. The association with maternal smoking appears limited to Hispanic children, raising questions about ethnic differences in tobacco-related exposures and biological mechanisms, as well as study-specific biases. [ABSTRACT FROM AUTHOR]

In the general population, evaluation of lung cancer risk from radon in houses is hampered by low levels of exposure and by dosimetric uncertainties due to residential mobility. To address these limitations, the authors conducted a case-control study in a predominantly rural area of China with low mobility and high radon levels. Included were all lung cancer cases diagnosed between January 1994 and April 1998, aged 30-75 years, and residing in two prefectures. Randomly selected, population-based controls were matched on age, sex, and prefecture. Radon detectors were placed in all houses occupied for 2 or more years during the 5-30 years prior to enrollment. Measurements covered 77% of the possible exposure time. Mean radon concentrations were 230.4 Bq/m³ for cases (n = 768) and 222.2 Bq/m³ for controls (n = 1,659). Lung cancer risk increased with increasing radon level (p < 0.001). When a linear model was used, the excess odds ratios at 100 Bq/m³ were 0.19 (95% confidence interval: 0.05, 0.47) for all subjects and 0.31 (95% confidence interval: 0.10, 0.81) for subjects for whom coverage of the exposure interval was 100%. Adjusting for exposure uncertainties increased estimates by 50%. Results support increased lung cancer risks with indoor radon exposures that may equal or exceed extrapolations based on miner data. Am J Epidemiol 2002;155:554-64. [ABSTRACT FROM AUTHOR]

Workers in the meat industry are exposed to viruses that cause leukemia and lymphoma in cattle and chickens, and also to carcinogenic chemical agents. This case-control study, nested in a cohort of members of a meatcutters' union in Baltimore, Maryland, investigated whether occupational exposures are associated with death from tumors of the hemopoietic and lymphatic systems. Cases of these tumors represent all deaths which occurred in the cohort between 1949 and 1980. Excess risks of tumors of the hemopoietic and lymphatic systems were observed throughout the meat industry, except in meatpacking plants. Slaughtering activities involving heavy exposure to oncogenic viruses were strongly associated with these tumors, especially with lymphomas. Thus, elevated risks were observed for butchers who killed animals (odds ratio (OR) = 5.3, 95% confidence interval (CI) 1.0–27.0); workers in chicken-slaughtering plants (OR = 3.3, 95% CI 0.8–13.1); and workers in cattle/sheep/pig abattoirs (OR = 2.8, 95% CI 0.8–9.5). Among supermarket workers, wrapping meat (mainly a female activity) was associated with increased risk of tumors of the hemopoietic and lymphatic systems (OR = 3.8, 95% CI 1.0–14.3), with the odds of both lymphomas and tumors of the myeloid stem cell being elevated. On the other hand, meatcutting in supermarkets (almost exclusively a male activity) was associated with multiple myeloma; the odds ratio for men was 18.0 (95% CI 1.6–207.5), with no myeloma cases being recorded in women. These associations persisted after limited control for exposures outside the industry that have also been observed to be associated with excess risk, such as exposure to pesticides, working/living on pig farms, and exposure to X-rays. The findings provide evidence that workers in the meat industry may be at elevated risk of tumors of the hemopoietic and lymphatic systems. Further studies with larger sample sizes are needed to identify more conclusively which exposures play an etiologic role in the occurrence of the different histologic types of these tumors. Am J Epidemiol 1998;147;727–38. [ABSTRACT FROM PUBLISHER]