Delayed infection, family size and malignant lymphomas

Birth Order, Sibship Size, Childhood Environment and Immune-Related Disorders, and Risk of Lymphoma in Lymphoid Cancer Families

BACKGROUND

Familial aggregation of lymphoid cancers and immune-related disorders suggests a role for genetic susceptibility; however, few studies examine environmental factors. According to the hygiene hypothesis, adult-onset immune-related diseases may be a consequence of reduced childhood infectious exposures and aberrant immune development. In a cohort of 196 multiple-case lymphoid cancer families, we analyzed environmental factors related to the hygiene hypothesis.

METHODS

Family structure, childhood environment, and immune-related disorders were examined among 196 lymphoid cancer families, in relation to risk of lymphoid cancer. We report on 450 lymphoid cancer cases and 1,018 unaffected siblings using logistic regression models with generalized estimating equations to estimate ORs and 95% confidence intervals (CI) for association.

RESULTS

The risk of lymphoma tended to decrease with later birth order (OR = 0.83; 95% CI, 0.78-0.89) and larger sibship size (OR = 0.82; 95% CI, 0.79-0.85). High maternal education, above average family income during childhood, allergies (OR = 2.25; 95% CI, 1.44-3.51), and tonsillectomy (OR = 1.78; 95% CI, 1.14-2.78) were independent risk factors for lymphoma. Familial lymphoid cancer cases were more likely to report environment (OR = 1.90; 95% CI, 1.21-2.98) and drug (OR = 2.30; 95% CI, 1.41-3.73) allergies.

CONCLUSIONS

These associations underscore the complex etiology of familial lymphoma. To our knowledge, this is the largest multiple-case family-based study that supports the hygiene hypothesis contributing to lymphoid cancer risk.

IMPACT

Understanding the mechanism by which environmental and lifestyle factors affect lymphoid cancer risk may advance cancer prevention, even in the familial context.

Childhood infectious diseases and risk of non-Hodgkin's lymphoma according to the WHO classification: A reanalysis of the Italian multicenter case-control study

Since 1960, incidence of non-Hodgkin's lymphoma (NHL) has been increasing in most industrialized countries, but causes of this trend remain unclear. A role of the decreased exposure to infectious agents during childhood has been proposed. Our study evaluates the association between common childhood infectious diseases and the risk of NHL and its major subtypes by a reanalysis of the Italian multicenter case-control study. After exclusion of next-of-kin interviews, 1,193 cases, diagnosed between 1990 and 1993, and 1,708 population-based controls were included in the analyses. OR estimates were obtained by logistic regression, adjusting for gender, age, residence area, education, smoking habit and exposure to radiations, pesticides and aromatic hydrocarbons. Among B-cell lymphomas (n = 1,102) an inverse association was observed for rubella (OR = 0.80, 95% CI: 0.65-0.99), pertussis (OR = 0.74, 95% CI: 0.62-0.88) and any infection (OR = 0.75, 95% CI: 0.61-0.93). A negative trend by number of infections was observed, which was more evident among mature B-cell lymphoma (OR = 0.66 for three infections or more, 95% CI: 0.48-0.90). Our results indicate a potential protective role of common childhood infections in the etiology of B-cell NHL.

Parental Age and Risk of Lymphoid Neoplasms

High parental age at childbirth has repeatedly been linked to childhood malignancies, while few studies have focused on the offspring's risk of adult cancer. In this population-based case-control study, we identified 32,000 patients with lymphoid neoplasms, diagnosed at ages 0-79 years during the period 1987-2011, and 160,000 matched controls in Sweden. Using prospectively registered data on their first-degree relatives, we evaluated the impact of parental age on the risk of lymphoid neoplasms by subtype. Overall, each 5-year increment in maternal age was associated with a 3% increase in incidence of offspring lymphoid neoplasms (hazard ratio = 1.03, 95% confidence interval: 1.02, 1.04). The association was similar for paternal age and present even among individuals older than 70 years of age at diagnosis. Stratified analyses further revealed that the association was limited to certain subtypes, mostly of indolent nature. Risks of chronic lymphocytic leukemia, follicular lymphoma, and mantle cell lymphoma were 5%-10% higher per 5-year increment in maternal age, but no associations were observed for acute lymphoblastic leukemia, plasma cell neoplasms, or diffuse large B-cell lymphoma. These findings indicated that prenatal genetic or epigenetic changes influence risk of adult lymphoid neoplasms and suggest a difference in this association between aggressive and indolent lymphoma subtypes.

Coffee and tea consumption and risk of leukaemia in an adult population: A reanalysis of the Italian multicentre case-control study

BACKGROUND

Coffee and tea are the most frequently consumed beverages in the world. Their potential effect on the risk of developing different types of malignancies has been largely investigated, but studies on leukaemia in adults are scarce.

METHODS

The present investigation is aimed at evaluating the potential role of regular coffee and tea intake on the risk of adult leukaemia by reanalysing a large population based case-control study carried out in Italy, a country with a high coffee consumption and a low use of green tea. Interviewed subjects, recruited between 1990 and 1993 in 11 Italian areas, included 1771 controls and 651 leukaemia cases. Association between Acute Myeloid Leukaemia (AML), Acute Lymphoid Leukaemia, Chronic Myeloid Leukaemia, Chronic Lymphoid Leukaemia, and use of coffee and tea was evaluated by standard logistic regression. Odds Ratios (OR) were estimated adjusting for the following potential confounders: gender, age, residence area, smoking habit, educational level, previous chemotherapy treatment, alcohol consumption and exposure to electromagnetic fields, radiation, pesticides and aromatic hydrocarbons.

RESULTS

No association was observed between regular use of coffee and any type of leukaemia. A small protective effect of tea intake was found among myeloid malignancies, which was more evident among AML (OR=0.68, 95%CI: 0.49-0.94). However, no clear dose-response relation was found.

CONCLUSION

The lower risk of leukaemia among regular coffee consumers, reported by a few of previous small studies, was not confirmed. The protective effect of tea on the AML risk is only partly consistent with results from other investigations.

Occupation and Risk of Non-Hodgkin Lymphoma and Its Subtypes: A Pooled Analysis from the InterLymph Consortium

BACKGROUND

Various occupations have been associated with an elevated risk of non-Hodgkin lymphoma (NHL), but results have been inconsistent across studies.

OBJECTIVES

We investigated occupational risk of NHL and of four common NHL subtypes with particular focus on occupations of a priori interest.

METHODS

We conducted a pooled analysis of 10,046 cases and 12,025 controls from 10 NHL studies participating in the InterLymph Consortium. We harmonized the occupational coding using the 1968 International Standard Classification of Occupations (ISCO-1968) and grouped occupations previously associated with NHL into 25 a priori groups. Odds ratios (ORs) adjusted for center, age, and sex were determined for NHL overall and for the following four subtypes: diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), and peripheral T-cell lymphoma (PTCL).

RESULTS

We confirmed previously reported positive associations between NHL and farming occupations [field crop/vegetable farm workers OR = 1.26; 95% confidence interval (CI): 1.05, 1.51; general farm workers OR = 1.19; 95% CI: 1.03, 1.37]; we also confirmed associations of NHL with specific occupations such as women's hairdressers (OR = 1.34; 95% CI: 1.02, 1.74), charworkers/cleaners (OR = 1.17; 95% CI: 1.01, 1.36), spray-painters (OR = 2.07; 95% CI: 1.30, 3.29), electrical wiremen (OR = 1.24; 95% CI: 1.00, 1.54), and carpenters (OR = 1.42; 95% CI: 1.04, 1.93). We observed subtype-specific associations for DLBCL and CLL/SLL in women's hairdressers and for DLBCL and PTCL in textile workers.

CONCLUSIONS

Our pooled analysis of 10 international studies adds to evidence suggesting that farming, hairdressing, and textile industry-related exposures may contribute to NHL risk. Associations with women's hairdresser and textile occupations may be specific for certain NHL subtypes.

CITATION

't Mannetje A, De Roos AJ, Boffetta P, Vermeulen R, Benke G, Fritschi L, Brennan P, Foretova L, Maynadié M, Becker N, Nieters A, Staines A, Campagna M, Chiu B, Clavel J, de Sanjose S, Hartge P, Holly EA, Bracci P, Linet MS, Monnereau A, Orsi L, Purdue MP, Rothman N, Lan Q, Kane E, Seniori Costantini A, Miligi L, Spinelli JJ, Zheng T, Cocco P, Kricker A. 2016. Occupation and risk of non-Hodgkin lymphoma and its subtypes: a pooled analysis from the InterLymph Consortium. Environ Health Perspect 124:396-405; http://dx.doi.org/10.1289/ehp.1409294.

Determinants of the t(14;18) translocation and their role in t(14;18)-positive follicular lymphoma

PURPOSE

The strong association between t(14;18) translocation and follicular lymphoma (FL) is well known. However, the determinants of this chromosomal aberration and their role in t(14;18) associated FL remain to be established.

METHODS

t(14;18) frequency within the B cell lymphoma 2 major breakpoint region was determined for 135 incident FL cases and 251 healthy controls as part of a nested case-control study within the European Prospective Investigation into Cancer cohort. Quantitative real-time PCR was performed in DNA extracted from blood samples taken at recruitment. The relationship between prevalence and frequency of the translocation with baseline anthropometric, lifestyle, and dietary factors in cases and controls was determined. Unconditional logistic regression was used to explore whether the risk of FL associated with these factors differed in t(14;18)(+) as compared to t(14;18)(-) cases.

RESULTS

Among incident FL cases, educational level (χ(2) p = 0.021) and height (χ(2) p = 0.025) were positively associated with t(14;18) prevalence, and cases with high frequencies [t(14;18)(HF)] were significantly taller (t test p value = 0.006). These findings were not replicated in the control population, although there were a number of significant associations with dietary variables. Further analyses revealed that height was a significant risk factor for t(14;18)(+) FL [OR 6.31 (95% CI 2.11, 18.9) in the tallest versus the shortest quartile], but not t(14;18)(-) cases.

CONCLUSIONS

These findings suggest a potential role for lifestyle factors in the prevalence and frequency of the t(14;18) translocation. The observation that the etiology of FL may differ by t(14;18) status, particularly with regard to height, supports the subdivision of FL by translocation status.

Season of birth and risk of Hodgkin and non-Hodgkin lymphoma

Infectious etiologies have been hypothesized for Hodgkin and non-Hodgkin lymphoma (HL and NHL) in early life, but findings to date for specific lymphomas and periods of susceptibility are conflicting. We conducted the first national cohort study to examine whether season of birth, a proxy for infectious exposures in the first few months of life, is associated with HL or NHL in childhood through young adulthood. A total of 3,571,574 persons born in Sweden in 1973-2008 were followed up through 2009 to examine the association between season of birth and incidence of HL (943 cases) or NHL (936 cases). We found a sinusoidal pattern in NHL risk by season of birth (p = 0.04), with peak risk occurring among birthdates in April. Relative to persons born in fall (September-November), odds ratios for NHL by season of birth were 1.25 [95% confidence interval (CI), 1.04-1.50; p = 0.02] for spring (March-May), 1.22 (95% CI, 1.01-1.48; p = 0.04) for summer (June-August) and 1.11 (95% CI, 0.91-1.35; p = 0.29) for winter (December-February). These findings did not vary by sex, age at diagnosis or major subtypes. In contrast, there was no seasonal association between birthdate and risk of HL (p = 0.78). In this large cohort study, birth in spring or summer was associated with increased risk of NHL (but not HL) in childhood through young adulthood, possibly related to immunologic effects of delayed infectious exposures compared with fall or winter birth. These findings suggest that immunologic responses in early infancy may play an important role in the development of NHL.

Occupational exposure to immunologically active agents and risk for lymphoma: the European Epilymph case-control study

OBJECTIVES

Allergies and asthma may be protective for the development of lymphoma. We evaluated whether occupational allergens that provoke immune reactivity and asthma through an IgE-mediated pathway are protective for lymphoma.

METHODS

The Epilymph study includes histologically or cytologically confirmed Hodgkin, B-cell, and T-cell lymphoma cases from six European countries (Spain, France, Germany, Italy, Ireland, and Czech Republic) recruited in 1998-2004. Controls were frequency matched to cases by age, gender, and study centre. Lifetime occupational exposure to seven high molecular weight (HMW) agents was evaluated through an asthma-specific job-exposure matrix. 2205 lymphoma cases and 2296 controls with complete occupational history could be included in the analysis. Associations between HMW exposures and lymphoma were evaluated using pooled unconditional logistic regression analyses.

RESULTS

Individuals exposed to HMW agents had a non-statistically significant decreased risk of any lymphoma (OR, 0.88: 95% CI, 0.74-1.05) and of B-cell lymphoma (OR, 0.91; 95% CI, 0.76-1.09), and a significantly decreased risk for Hodgkin lymphoma (OR, 0.62; 95% CI, 0.40-0.98). A decrease in risk for lymphoma was found for exposure to latex (OR, 0.74; 95% CI, 0.55-0.99).

CONCLUSIONS

Further epidemiologic and mechanistic research is needed to confirm that occupational exposure to HMW agents predisposing to asthma can reduce the risk of lymphoma.

Perinatal and family risk factors for Hodgkin lymphoma in childhood through young adulthood

The incidence of Hodgkin lymphoma has increased among adolescents and young adults in recent decades, but the relevant risk factors in early life are still unknown. A national cohort study was conducted of 3,571,574 individuals born in Sweden in 1973-2008 and followed up for Hodgkin lymphoma incidence through 2009, to examine perinatal and family risk factors for Hodgkin lymphoma in childhood through young adulthood (ages 0-37 years). There were 943 Hodgkin lymphoma cases identified in 66.3 million person-years of follow-up. High fetal growth was associated with an increased risk of Hodgkin lymphoma after adjustment for gestational age at birth and other potential confounders (P(trend) = 0.005). Family history of Hodgkin lymphoma in a sibling or parent also was strongly associated with an increased risk, with adjusted hazard ratios = 8.83 (95% confidence interval: 3.67, 21.30) and 7.19 (95% confidence interval: 3.58, 14.44), respectively. No association was found between gestational age at birth, birth order, twinning, parental age, or parental education and Hodgkin lymphoma. These findings did not vary by age at Hodgkin lymphoma diagnosis. Similar associations were found for nodular sclerosis and mixed cellularity subtypes. These findings suggest that perinatal factors including possible growth factor pathways may contribute to the risk of Hodgkin lymphoma in childhood through young adulthood.

Lymphoma risk in livestock farmers: results of the Epilymph study

We explored the risk of lymphoma and its most prevalent subtypes associated with occupational contact with livestock, and whether risk was modified by age at first contact, in 2,348 incident lymphoma cases and 2,462 controls who participated in the EPILYMPH case-control study. A detailed occupational history was collected in cases and controls, including working in a livestock farm, species of livestock, its approximate number and circumstances of contact. For each disease outcome, and each type of livestock, odds ratios (OR) and their 95% confidence intervals (95% CI) were calculated using unconditional logistic regression, adjusting for age, gender, education and center. Lymphoma risk (all subtypes combined) was not increased amongst those exposed to contact with any livestock (OR = 1.0, 95% CI 0.8-1.2). Overall, we did not observe an association between occupational contact with livestock and risk of lymphoma (all types) and B-cell lymphoma. The risk of diffuse large B cell lyphoma (DLBCL) was significantly lower amongst subjects who started occupational contact with any species of livestock before or at age 12 (OR = 0.5, 95% CI 0.2-0.9), but not at older ages. A significant heterogeneity in risk of B cell lymphoma by age at first contact was detected for contact with cattle, poultry and swine. Early occupational contact with livestock might be associated with a decrease in risk of B cell lymphoma.

Current understanding of lifestyle and environmental factors and risk of non-hodgkin lymphoma: an epidemiological update

The incidence rates of non-Hodgkin lymphoma (NHL) have steadily increased over the last several decades in the United States, and the temporal trends in incidence can only be partially explained by the HIV epidemic. In 1992, an international workshop sponsored by the United States National Cancer Institute concluded that there was an “emerging epidemic” of NHL and emphasized the need to investigate the factors responsible for the increasing incidence of this disease. Over the past two decades, numerous epidemiological studies have examined the risk factors for NHL, particularly for putative environmental and lifestyle risk factors, and international consortia have been established in order to investigate rare exposures and NHL subtype-specific associations. While few consistent risk factors for NHL aside from immunosuppression and certain infectious agents have emerged, suggestive associations with several lifestyle and environmental factors have been reported in epidemiologic studies. Further, increasing evidence has suggested that the effects of these and other exposures may be limited to or stronger for particular NHL subtypes. This paper examines the progress that has been made over the last twenty years in elucidating the etiology of NHL, with a primary emphasis on lifestyle factors and environmental exposures.

Perinatal and family risk factors for non-Hodgkin lymphoma in early life: a Swedish national cohort study

BACKGROUND

The incidence of non-Hodgkin lymphoma (NHL) in early life has increased in recent decades, but the relevant risk factors remain largely unknown. We examined perinatal and family risk factors for NHL in childhood through young adulthood.

METHODS

We conducted a national cohort study of 3 571 574 individuals born in Sweden in 1973-2008 who were followed for incidence of NHL through 2009 (ages 0-37 years). Detailed information on perinatal and family characteristics and NHL diagnoses were obtained from national birth and cancer registries. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between perinatal and family variables and NHL; P values are from two-sided tests.

RESULTS

There were 936 NHL case patients identified in 66.3 million person-years of follow-up. Independent risk factors for NHL included family history of NHL in either a sibling (adjusted HR = 9.84; 95% CI = 2.46 to 39.41; P = .001) or parent (adjusted HR = 2.36; 95% CI = 1.27 to 4.38; P = .007); high fetal growth (for ≥ 2 SDs relative to 0 to <1 SD from the mean: adjusted HR = 1.64; 95% CI = 1.19 to 2.25; P = .002); older maternal age (adjusted HR for each 5-year increment = 1.11; 95% CI = 1.04 to 1.19; P (trend) = .004); low birth order (adjusted HR for each increment of one birth = 0.91; 95% CI = 0.84 to 0.99; P (trend) = .02); and male sex (adjusted HR = 1.58; 95% CI = 1.38 to 1.80; P < .001). Male sex was associated with onset of NHL before 15 years of age but not with later-onset NHL, whereas the other risk factors did not vary by age at diagnosis. No association was found between gestational age at birth, twinning, paternal age, or parental education and NHL.

CONCLUSION

In this large national cohort study, family history of NHL, high fetal growth, older maternal age, low birth order, and male sex were independent risk factors for NHL in early life.

A prospective study of organochlorines in adipose tissue and risk of non‑Hodgkin lymphoma

BACKGROUND

Exposure to organochlorines has been examined as a potential risk factor for non-Hodgkin lymphoma (NHL), with inconsistent results that may be related to limited statistical power or to imprecise exposure measurements.

OBJECTIVE

Our purpose was to examine associations between organochlorine concentrations in prediagnostic adipose tissue samples and the risk of NHL.

METHODS

We conducted a case–cohort study using a prospective Danish cohort of 57,053 persons enrolled between 1993 and 1997. Within the cohort we identified 256 persons diagnosed with NHL in the population-based nationwide Danish Cancer Registry and randomly selected 256 subcohort persons. We measured concentrations of 8 pesticides and 10 polychlorinated biphenyl (PCB) congeners in adipose tissue collected upon enrollment. Associations between the 18 organochlorines and NHL were analyzed in Cox regression models, adjusting for body mass index.

RESULTS

Incidence rate ratios and confidence intervals (CIs) for interquartile range increases in concentrations of dichlorodiphenyltrichlorethane (DDT), cis-nonachlor, and oxychlordane were 1.35 (95% CI: 1.10, 1.66), 1.13 (95% CI: 0.94, 1.36), and 1.11 (95% CI: 0.89, 1.38), respectively, with monotonic dose–response trends for DDT and cis-nonachlor based on categorical models. The relative risk estimates were higher for men than for women. In contrast, no clear association was found between NHL and PCBs.

CONCLUSION

We found a higher risk of NHL in association with higher adipose tissue levels of DDT, cis-nonachlor, and oxychlordane, but no association with PCBs. This is the first study of organochlorines and NHL using prediagnostic adipose tissue samples in the exposure assessment and provides new environmental health evidence that these organochlorines contribute to NHL risk.

Epidemiologic perspective on immune-surveillance in cancer

Common 'themes' in epidemiology related to cancer risk beg a comprehensive mechanistic explanation. As people age, risk for cancer increases. Obesity and smoking increase the risk for many types of cancer. History of febrile childhood diseases lowers the risk for melanomas, leukemias, non-Hodgkin's lymphoma (NHL), and ovarian cancer. Increasing number of ovulatory cycles uninterrupted by pregnancies correlate positively with breast, endometrial, and ovarian cancer risk while pregnancies and breastfeeding lower the risk for these cancers as well as cancers of the colon, lung, pancreas, and NHL. Chronic inflammatory events such as endometriosis or mucosal exposure to talc increase the risk for several types of cancer. Mechanisms so far considered are site specific and do not explain multiple associations. We propose that most of these events affect cancer immunosurveillance by changing the balance between an effective immune response and immune tolerance of an emerging cancer. We review recently published data that suggest that immune mechanisms underlie most of these observed epidemiologic associations with cancer risk.

Household contact with pets and birds and risk of lymphoma

BACKGROUND

Contact with household pets has been suggested to be inversely associated with lymphoma risk.

METHODS

We tested the hypothesis in a case-control study of lymphoma in the Sardinia region of Italy. Cases were 326 patients, first diagnosed with lymphoma in 1999-2003. Controls were 464 population controls, frequency matched to cases by age, gender, and area of residence. In person interviews included self-reported household contact with pets and birds, type of pet(s), and age at starting contact.

RESULTS

Frequent contact with birds was inversely associated with lymphoma, and particularly B-cell non-Hodgkin lymphoma (odds ratio [OR] = 0.6, 95% confidence interval [95% CI]: 0.4, 0.9). Contact with chickens accounted for this inverse association, which was strongest for first contact occurring at age ≤8 years (OR = 0.4, 95% CI: 0.2, 1.0). No association was observed when first contact occurred at age 9 or older. Contact with any pets was inversely associated with risk of diffuse large B-cell lymphoma (OR = 0.4, 95% CI: 0.2, 1.0), but not other lymphoma subtypes.

CONCLUSION

Our results support the hypothesis that early-life exposure to pets, birds and particularly with chickens might be associated with a reduced risk of lymphoma.

Birth order and risk of non-hodgkin lymphoma--true association or bias?

There is inconsistent evidence that increasing birth order may be associated with risk of non-Hodgkin lymphoma (NHL). The authors examined the association between birth order and related variables and NHL risk in a pooled analysis (1983-2005) of 13,535 cases and 16,427 controls from 18 case-control studies within the International Lymphoma Epidemiology Consortium (InterLymph). Overall, the authors found no significant association between increasing birth order and risk of NHL (P-trend = 0.082) and significant heterogeneity. However, a significant association was present for a number of B- and T-cell NHL subtypes. There was considerable variation in the study-specific risks which was partly explained by study design and participant characteristics. In particular, a significant positive association was present in population-based studies, which had lower response rates in cases and controls, but not in hospital-based studies. A significant positive association was present in higher-socioeconomic-status (SES) participants only. Results were very similar for the related variable of sibship size. The known correlation of high birth order with low SES suggests that selection bias related to SES may be responsible for the association between birth order and NHL.

Delayed exposure to infections and childhood lymphomas: a case-control study

OBJECTIVES

Delayed exposure to common infections during childhood, have been implied to cause strong immunological response to a single infectious agent that eventually triggers leukemogenesis. The aim of the present study was to investigate whether decreased exposure to infections, as reflected in a more seronegative spectrum to several common infectious agents, is associated with increased risk for the development of childhood lymphomas.

METHODS

All 125 children (up to 14 years old), with Hodgkin (HL, n = 52) and non-Hodgkin lymphomas (NHL, n = 73) diagnosed through the national network of childhood Hematology-Oncology units during an 8-year period were enrolled in the study along with 125 age- and gender-matched controls. Past exposure to nine common infections [respiratory syncytial virus (RSV), influenza A and B, parainfluenza type 1, adenovirus, Epstein-Barr virus (EBV), cytomegalovirus (CMV), human herpes virus 6 (HHV6), Bartonella henselae] was assessed using serological markers.

RESULTS

After controlling for possible confounding factors, the overall seronegativity status upon diagnosis was statistically significantly associated with NHL [odds ratio; 95% CI: 1.45 (1.10-1.93), p = 0.01] and less so with HL risk [odds ratio; 95% CI: 1.30 (0.83-2.05), p = 0.25]. A statistically significant association of seronegativity with the development of NHL was evident for RSV [odds ratio; 95% CI: 7.27 (1.59-33.28), p = 0.01], EBV [odds ratio; 95% CI: 6.73 (1.45-31.20), p = 0.01] and suggestive association for influenza B [odds ratio; 95% CI: 2.60 (0.90-7.55), p = 0.08] and influenza A [odds ratio; 95% CI: 2.35 (0.81-6.80), p = 0.11]. In contrast, there was no evidence for association of HL with negative serology for any of the infectious agents tested.

CONCLUSIONS

The risk of lymphomas, especially NHL, might be higher when, due to lower exposure to several infectious agents, the relatively unmodulated immune system of a child is challenged by environmental stimuli that can trigger development of lymphomas. The results, however, need further confirmation, through more pertinent methodological designs.

Racial/ethnic variation in EBV-positive classical Hodgkin lymphoma in California populations

Epstein-Barr virus (EBV) is detected in the tumor cells of some but not all Hodgkin lymphoma (HL) patients, and evidence indicates that EBV-positive and -negative HL are distinct entities. Racial/ethnic variation in EBV-positive HL in international comparisons suggests etiologic roles for environmental and genetic factors, but these studies used clinical series and evaluated EBV presence by differing protocols. Therefore, we evaluated EBV presence in the tumors of a large (n = 1,032), racially and sociodemographically diverse series of California incident classical HL cases with uniform pathology re-review and EBV detection methods. Tumor EBV-positivity was associated with Hispanic and Asian/Pacific Islander (API) but not black race/ethnicity, irrespective of demographic and clinical factors. Complex race-specific associations were observed between EBV-positive HL and age, sex, histology, stage, neighborhood socioeconomic status (SES), and birth place. In Hispanics, EBV-positive HL was associated not only with young and older age, male sex, and mixed cellularity histology, but also with foreign birth and lower SES in females, suggesting immune function responses to correlates of early childhood experience and later environmental exposures, respectively, as well as of pregnancy. For APIs, a lack of association with birth place may reflect the higher SES of API than Hispanic immigrants. In blacks, EBV-positive HL was associated with later-stage disease, consistent with racial/ethnic variation in certain cytokine polymorphisms. The racial/ethnic variation in our findings suggests that EBV-positive HL results from an intricate interplay of early- and later-life environmental, hormonal, and genetic factors leading to depressed immune function and poorly controlled EBV infection.

Childhood social environment and risk of non-Hodgkin lymphoma in adults

Better hygiene and sanitation and decreasing family size parallel the increasing incidence of non-Hodgkin lymphoma (NHL) in many populations around the world. However, whether sibship size, birth order, and crowding are related to adult NHL risk is not clear. We investigated how family structure and childhood social environment were related to the risk of NHL and NHL subtypes in a large Scandinavian population-based case control study with 6,242 participants aged 18 to 74 years. Detailed exposure information was obtained through telephone interviews. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using logistic regression, and all statistical tests were two-sided. Having four or more siblings was associated with a moderately increased risk of NHL, compared with having no siblings (OR 1.34, 95% CI 1.11-1.62, P(trend) < 0.001). Having four or more older siblings was associated with a similar risk increase (OR 1.33, 95% CI 1.12-1.59, P(trend) = 0.003) compared with being the oldest, whereas number of younger siblings was unrelated overall. The associations were independent of other environmental exposures and did not vary by country, age, or sex. High household crowding was also positively associated with risk of NHL. Results were slightly stronger for diffuse large B-cell and T-cell lymphomas than for other major NHL subtypes. Our findings add to the evidence that large sibship size, late birth order, and childhood crowding are associated with an elevated risk of NHL. Effect mechanisms may be related to early age at onset and high frequency of specific infections or total microbial exposure in childhood.

The effect of atopy, childhood crowding, and other immune-related factors on non-Hodgkin lymphoma risk

OBJECTIVE

Since adult immune responsiveness is influenced by early childhood exposures, we examined the role of family size, history of atopic disease, and other childhood immune-related exposures in a multi-center case-control study of NHL.

METHODS

Interviews were completed with 1,321 cases ascertained from population-based cancer registries in Seattle, Detroit, Los Angeles and Iowa, and with 1,057 frequency-matched controls, selected by random-digit dialing and from the Medicare files database. Multivariable logistic regression was used to estimate risk.

RESULTS

A history of any allergy (excluding drug allergies), decreased risk of all NHL (Odds Ratio [OR] = 0.7, 95% Confidence Interval [CI] = 0.6-1.0), diffuse large B-cell lymphoma [DLBCL] (OR = 0.6, 95% CI = 0.4-0.9), and follicular NHL (OR = 0.7, 95 CI = 0.5, 1.0). A similar effect was observed for hay fever. A history of eczema was associated with an increased risk of follicular lymphoma (OR = 1.9, 95% CI = 1.1-3.4), but not DLBCL (OR = 1.1, 95% CI = 0.6-2.0). Asthma did not affect risk. Youngest compared to oldest siblings had a 90% increased risk of DLBCL (95% CI = 1.2-3.1; p for trend with increasing birth order = 0.006), but not follicular lymphoma (OR = 1.1, 95% CI = 0.6-1.8).

CONCLUSIONS

We infer that some childhood and immune-related factors may alter NHL risk.

Birth order, allergies and lymphoma risk: results of the European collaborative research project Epilymph

Lymphomas are a heterogeneous group of malignancies of the immune system. Recent studies suggest that immunological conditions which are modulated by lifestyle-dependent environmental determinants might affect lymphoma risk. We used data from Epilymph, a European multi-centric case-control study with 2,480 cases and 2,540 controls, to analyse the relationship between lifestyle-dependent immunological determinants and risk of lymphomas. We found an inverse relationship between risk of lymphoma and allergies, mainly respiratory (OR=0.86, CI=0.89-1.01) and food allergies (OR=0.67, CI=0.52-0.85), a slightly elevated lymphoma risk for first-born children (OR=1.17, CI=0.99-1.39) and only children (OR=1.10, CI=0.86-1.39). The inverse relationship between atopic disorders and risk of lymphomas is consistent with earlier observations. Our findings on birth order and lymphoma increase the inconsistency of findings across studies and suggest a critical reappraisal of potential underlying mechanisms.

Alcohol consumption and risk of leukemia: A multicenter case–control study

A population-based case-control study of 649 leukemia cases and 1771 controls carried out in 11 Italian areas, offered the opportunity to evaluate the relationship between alcohol consumption and leukemia risk. For all leukemias, acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML), and chronic lymphocytic leukemia (CLL), we found a non-significantly inverse association for moderate levels of total alcohol and wine intake, but increased risks at high levels, with, in most cases, significant trend effects (odd ratios (OR) for all leukemias in the lowest quartile of total alcohol consumption [0.1-9.0 g/day of ethanol] versus never-drinker = 0.73; 95% confidence intervals (95% CI) = 0.51-1.03; OR in the highest quartile [> 31.7 g/day] = 1.15; 95% CI = 0.82-1.63; p of the linear trend test = 0.007). For chronic myeloid leukemia (CML), we found a non-significantly positive association for all levels of total alcohol and wine intake, and a significant positive linear trend effect (p = 0.03) for wine intake (OR for 0.1-9.0 g/day of ethanol intake from wine = 1.34; 95% CI = 0.61-2.94; OR in the highest quartile of wine intake [> 27.7 g/day] = 2.13; 95% CI = 1.01-4.50). No consistent dose-response was detected analysing duration of alcohol consumption for any leukemia subtypes. In conclusion, even though our study did not show a clear association between alcohol intake and leukemia risk, some of the patterns of the risk estimates (a possible J-shaped dose-response curve between alcohol intake and ALL, AML, and CLL risks, and the positive association between alcohol and CML), may be suggestive.

Residential history, family characteristics and non-Hodgkin lymphoma, a population-based case-control study in the San Francisco Bay Area

A population-based, case-control study (N = 1,593 cases, N = 2,515 controls) was conducted in the San Francisco Bay Area, California, to determine risk factors for non-Hodgkin lymphoma (NHL). This report examines residential characteristics, number of siblings, childhood infections, and allergic rhinitis to evaluate the association between NHL and the hygiene hypothesis. Adjusted unconditional logistic regression analyses included HIV-negative participants (N = 1,304 cases, N = 2,402 controls) ages 21 to 74 years, who completed in-person interviews. At childhood ages, odds ratios (OR) for NHL decreased with increasing number of household rooms (age 8 years, P(trend) = 0.08; age 15 years, P(trend) < 0.0001) and increased with more crowded living conditions (quartiles of no. people/no. rooms; age 8 years, P(trend) < 0.0001; age 15 years, P(trend) = 0.0004), whereas at older ages a greater number of people in the household and greater number of household rooms were positively associated with NHL. ORs increased with increasing number of siblings (P(trend) = 0.0003) and increasing birth order (P(trend) = 0.01). Participants with five or more younger siblings had a 50% increased OR for NHL. ORs for NHL decreased with an increasing number of different infections during childhood (age 8 years, P(trend) < 0.0001; age 15 years, P(trend) = 0.0003) and with history of allergic rhinitis (P < 0.0001). Our results are somewhat consistent with the hygiene hypothesis that less crowding and better sanitation results in fewer infections early in life and an increased incidence of immune-related conditions later in life. The role of the complex relationship between residential history, family characteristics, childhood infections, and immune function in the development of NHL warrants further investigation in pooled analyses.

Specific infections, infection-related behavior, and risk of non-Hodgkin lymphoma in adults

Infections were examined as possible risk factors for non-Hodgkin lymphoma in a population-based case-control study in New South Wales and the Australian Capital Territory, Australia. Incident cases (n = 694) had no history of HIV infection or transplantation. Controls (n = 694) were randomly selected from electoral rolls and frequency matched to cases by age, sex, and area of residence. A postal questionnaire and telephone interview measured history of specific infections, occupational exposures, and behavioral and other risk factors for infection. Blood samples were tested for antibodies to human T-lymphotrophic virus type I and hepatitis C virus. Logistic regression models included the three matching variables and ethnicity. There was no association between risk of non-Hodgkin lymphoma and any of the variables analyzed, including sexually transmitted infections, sexual behavior, blood transfusions, influenza, acne, and either occupational or domestic exposure to zoonotic infections. Non-Hodgkin lymphoma risk was nonsignificantly elevated (odds ratio, 2.99; 95% confidence interval, 0.78-11.51) for those with a history of injecting drug use. Three cases and two controls (odds ratio, 1.32; 95% confidence interval, 0.22-7.98) tested positive to hepatitis C virus infection and none tested positive to human T-lymphotrophic virus type I/II infection. This study provides consistent evidence that sexually transmitted infections and zoonoses are not risk factors for non-Hodgkin lymphoma.

Alcohol consumption and risk of Hodgkin's lymphoma and multiple myeloma: a multicentre case-control study

BACKGROUND

Few studies have analysed the association between alcohol intake and Hodgkin's lymphoma (HL) or multiple myeloma (MM) risks.

MATERIALS AND METHODS

A multicentre population-based case-control study of 363 HL, 270 MM cases, and 1771 controls offered the opportunity to evaluate the relationship between alcohol and HL/MM risks. Unconditional logistic regression was carried out to estimate odds ratios (ORs) and 95% confidence intervals (CIs), associated with alcohol intake (servings per week, grams per day of ethanol intake) or duration of exposure (year).

RESULTS

For HL, considering nonsmokers only, ever drinkers had a significantly decreased risk than never drinkers (OR=0.46). Significantly lower risks in all levels of total alcohol intake were also detected, considering servings per week (OR for one to four servings per week=0.51, 95% CI 0.32-0.82; OR for five to nine servings per week=0.39, 95% CI 0.21-0.73; OR for 10-19 servings per week=0.26, 95% CI 0.12-0.54; OR for >or=20 servings per week=0.34, 95% CI 0.15-0.79) and grams per day of ethanol intake (OR for 0.1-9.0 g/day=0.45, 95% CI 0.27-0.74; OR for 9.1-17.9 g/day=0.52, 95% CI 0.30-0.90; OR for 18.0-31.7 g/day=0.27, 95% CI 0.13-0.57; OR for >31.7 g/day=0.35, 95% CI 0.15-0.79). In the analysis for ever-smoking HL cases and controls, ever drinkers had the same risk as never drinkers. For MM, ever drinkers had a non-significantly decreased risk than non-drinkers (OR=0.74), and ORs in almost all consumption levels were not significant (OR for 0.1-9.0 g/day=0.93; OR for 9.1-17.9 g/day=0.82; OR for 18.0-31.7 g/day=0.47; 95% CI 0.28-0.81; OR for >31.7 g/day=0.68). For HL and MM, the beverage type did not affect the risk significantly, and no consistent dose-response relationships were found, considering intensity or duration of alcohol consumption.

CONCLUSIONS

Our study indicates a protective effect of alcohol consumption for nonsmoking HL cases.

Gene polymorphisms in Toll-like receptors, interleukin-10, and interleukin-10 receptor alpha and lymphoma risk

Interactions between environment and immune system play an essential role in the aetiology of immunopathologies, including lymphomas. Toll-like receptors (TLR) belong to a group of pattern recognition receptors, with importance for innate immune response and inflammatory processes. Interleukin-10 (IL-10) is a key regulatory cytokine and has been implicated in lymphomagenesis. Functional polymorphisms in these inflammation-associated genes may affect the susceptibility towards lymphoma. To test this hypothesis, we have genotyped DNA of 710 lymphoma cases and 710 controls within the context of a population-based epidemiological study for 11 functionally important single-nucleotide polymorphisms in TLR1, -2, -4, -5, -9, IL10 and IL10 receptor (IL10RA). The IL10RA Ser138Gly variant was underrepresented among lymphoma cases (odds ratio (OR)=0.81, 95 per cent confidence interval (95% CI)=0.65-1.02), mainly owing to an inverse association with Hodgkin's lymphoma (HL). The TLR2 -16933T>A variant was associated with a 2.8-fold increased risk of follicular lymphoma (95% CI=1.43-5.59) and a decreased risk of chronic lymphocytic leukaemia (OR=0.61, 95% CI=0.38-0.95). Furthermore, the TLR4 Asp299Gly variant was positively associated with the risk of mucosa-associated lymphoid tissue lymphoma (OR=2.76, 95% CI=1.12-6.81) and HL (OR=1.80, 95% CI=0.99-3.26). In conclusion, this study suggests an effect of polymorphisms in factors of the innate immune response in the aetiology of some lymphoma subtypes.

Do childhood diseases affect NHL and HL risk? A case-control study from northern and southern Italy

To investigate the association between non-Hodgkin lymphoma (NHL), Hodgkin lymphoma (HL), and exposure to childhood diseases, we analyzed an Italian case-control study that included 225 histologically-confirmed incident cases of NHL, 62 HL cases, and 504 controls. After adjusting for confounding factors, all examined childhood diseases were negatively associated with HL. Measles was negatively associated with NHL, particularly follicular B-cell NHL. Our findings provide additional support to the hypothesis that infections by most common childhood pathogens may protect against HL or, at least, be correlated with some other early exposure, which may lower the risk of HL in adulthood. In addition, our study shows that measles may provide a protective effect against NHL.

A marine fish diet reduces spontaneous lymphoma in outbred Swiss-Webster mice

Diets rich in marine organisms or their oils are known to suppress solid tumor development in humans and rodents, but the potential for marine foods to affect hematopoietic system cancers is not well understood. As part of a toxicology study, we fed groups of mice three different diets for 10 weeks: marine fish, 58% homogenized Atlantic smelt and herring; freshwater fish, 58% smelt and alewife from the North American Great Lakes, and commercial dry rodent chow. Between 1 and 15 weeks following dietary treatment, 20 of 103 (19.4%) mice unexpectedly developed spontaneous lymphoma. Disease incidence peaked when the mice were 7-8 months old, and was not distributed equally across treatment groups. Mice in the control (30%) and fresh water fish (27.5%) groups had significantly higher incidences of lymphoma than those fed Atlantic fish species (5%). Although our experiment was not originally designed for this purpose, our results indicate that consumption of fat-rich Atlantic smelt and herring protected mice against hematopoietic tumor development.

Prediagnostic Circulating Antibodies to JC and BK Human Polyomaviruses and Risk of Non-Hodgkin Lymphoma

Viral infections have been associated with increased risk of non-Hodgkin's lymphoma (NHL). We conducted a nested case-control study to investigate the association between prediagnostic serum antibodies to the human polyomaviruses, JC (JCV) and BK (BKV), and subsequent risk of NHL. Two research serum banks were established in Washington County, Maryland, in 1974 and 1989, with the collection of blood samples from >45,000 volunteers. Incident NHL cases diagnosed through 2002 (n = 170) were identified among participants by linkage to population-based cancer registries. Two controls were matched to each case (n = 340) on age, sex, and blood draw date. Prediagnostic IgG antibodies to JCV and BKV were measured using virus-like particle ELISA. Associations between JCV and BKV antibody seropositivity and NHL were estimated using conditional logistic regression. Overall, neither antibodies to JCV [odds ratio (OR), 0.83; 95% confidence interval (95% CI), 0.56-1.23] nor BKV (OR, 0.98; 95% CI, 0.64-1.48) were associated with an increased risk of NHL. Results were similar after stratification by NHL subtype or induction period and adjustment for EBV seropositivity. Among those who donated blood in both 1974 and 1989, an increase in JCV antibody levels over time was associated with a 4-fold increased risk of NHL compared with a steep decline in antibody levels (OR, 4.59; 95% CI, 1.30-16.25; P(trend) = 0.02). Whereas JCV seropositivity was not associated with NHL overall, the finding of an increased risk of NHL associated with increasing antibody levels among those who were seropositive at baseline warrants further research into factors influencing reactivation of JCV infection.

The epidemiology of non-Hodgkin lymphoma

Non-Hodgkin lymphoma (NHL) includes a group of more than 20 different malignant lymphoproliferative diseases that originate from lymphocytes. Rates of NHL have increased dramatically over the past few decades, although the rate of increase has recently slowed. It is now the sixth most common cancer in Australia. Globally, it is somewhat more common in men than in women, and rates are highest in North America and Australia. The causes of the increase in NHL rates are largely unknown. The best described risk factor for NHL is immune deficiency; rates of NHL are greatly increased, with relative risks of 10-100 or more, in people with immune deficiency associated with immune suppressive therapy after transplantation, HIV/AIDS, and congenital conditions. In addition, some NHL subtypes are associated with specific infections. These include immune-deficiency-associated central nervous system NHL (Epstein-Barr virus); gastric mucosa-associated lymphoid tissue NHL (Helicobacter pylori); adult T-cell leukemia/lymphoma (human T-lymphotrophic virus type 1) and body cavity-based lymphoma (human herpesvirus 8). However, these specific infections account for a very small proportion of total NHL incidence. In addition to immune deficiency and infection, other immune-related conditions are increasingly being recognised as related to NHL risk. Specific autoimmune conditions, including rheumatoid arthritis, systemic lupus erythema, Sjogren's syndrome, psoriasis and coeliac disease are associated with moderately increased risk of NHL. On the other hand, allergic and atopic conditions and their correlates such as early birth order, appear to be associated with a decreased risk of NHL.A variety of other exposures are less strongly related to NHL risk. These include occupational exposures, including some pesticides, herbicides, and solvents. Recently, two studies have reported that sun exposure is associated with a decreased risk of NHL. Smoking appears to be weakly positively associated with risk of follicular NHL, and alcohol intake is associated with a decreased risk of NHL. The pooled analysis of several case-control studies of NHL risk that are currently in the field promises to help clarify which of these risk factors are real, and will contribute to the elucidation of the mechanisms of how disorders of the immune system, and other factors, are related to NHL risk.

Neighborhood Socioeconomic Status and Hodgkin's Lymphoma Incidence in California

Hodgkin's lymphoma occurrence has long been noted to associate with higher socioeconomic status (SES). However, the Hodgkin's lymphoma-SES association has not been examined recently or across important, possibly etiologically distinct, patient subgroups. In approximately 150 million person-years of observation in the multiethnic population of California, we examined the association of Hodgkin's lymphoma incidence with a composite measure of neighborhood-level SES in patient subgroups defined by age, sex, race/ethnicity, and Hodgkin's lymphoma histologic subtype. Using population-based cancer registry data on 3,794 Hodgkin's lymphoma patients diagnosed 1988 to 1992 and 1990 census data, we assigned a previously validated, multidimensional SES index to census block groups of patient residence. We then calculated neighborhood SES-specific incidence rates and estimated rate ratios using Poisson regression. Positive neighborhood SES gradients in Hodgkin's lymphoma incidence were observed only in young adults (ages 15-44 years at diagnosis) with nodular sclerosis Hodgkin's lymphoma and older adult (ages > or =45 years) White and Hispanic males with mixed cellularity Hodgkin's lymphoma. For young adults, associations were marked in Hispanic and Asian women, weaker in Hispanic and White men and White women, and subtle to nonexistent in Blacks and Asian men. Neighborhood SES gradients in Hodgkin's lymphoma incidence varied by age, sex, race/ethnicity, and histologic subtype, underscoring etiologic complexity in Hodgkin's lymphoma. Racial/ethnic gradients were not entirely explained by neighborhood SES. In California, etiologically relevant exposures for young adult Hodgkin's lymphoma, the most common form, could associate more with race/ethnicity or foreign birthplace than neighborhood SES and may be modified by reproductive or other sex-specific factors.

Birth order, atopy, and risk of non-Hodgkin lymphoma

BACKGROUND

Immune deficiency is a strong risk factor for non-Hodgkin lymphoma (NHL), but whether or not other forms of immune dysregulation are associated with NHL risk is unknown. We investigated associations between atopy, which is associated with a Th2-dominant immune response, and NHL risk. Because late birth order and childhood crowding are inversely associated with atopy, we also investigated their associations with NHL risk.

METHODS

We carried out a population-based case-control study among adults aged 20-74 years in New South Wales and the Australian Capital Territory, Australia. NHL patients without clinically apparent immune deficiency (N = 704) were selected from a cancer registry, and control subjects (N = 694) were randomly selected from state electoral rolls and frequency-matched to case patients by age, sex, and area of residence. Birth order, childhood crowding, and history of atopic conditions (hay fever, asthma, eczema, and specific allergies) were assessed by questionnaire and interview. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated from logistic regression models that included the matching variables as covariates.

RESULTS

The odds ratios for developing NHL were 0.52 (95% CI = 0.32 to 0.84) for only children, 0.55 (95% CI = 0.40 to 0.75) for first-born children, 0.70 (95% CI = 0.51 to 0.96) for second-born children, and 0.81 (0.57 to 1.14) for third-born children (all compared with fourth- or later-born children) (P(trend)<.001). Indicators of crowding in later childhood, such as sharing a bed or bedroom, were not associated with NHL risk. A history of atopic conditions was associated with a reduced risk of NHL; this reduction was statistically significant for hay fever (OR = 0.65, 95% CI = 0.52 to 0.82) and food allergies (OR = 0.29, 95% CI = 0.20 to 0.42).

CONCLUSIONS

Early birth order and its immunologic consequence, a Th2-dominated immune response, as reflected by a history of atopic disease, are associated with a reduced risk of NHL.

Medical history and risk for lymphoma: results of a population-based case-control study in Germany

Since lymphomas are malignancies of cells of the immune system, associations with disorders characterised by impaired immune functions can be assumed. We investigated the relationship between a history of selected medical conditions and the risk for lymphoma including specified subentities within our population-based case-control study of lymphoma among adults conducted in Germany between 1999 and 2002. Overall, we found decreased risks for a history of repeated diarrhoea, warts, arthrosis, allergies, and appendectomy (at a younger age). Elevated risks for lymphoma correlated with tonsillectomy (at a younger age), whereas null results were found for selected auto-immune disorders in adulthood. Although the numbers are small, most of the results for the subentities corresponded with these findings. These results are compatible with the notion that persistent immunological alterations contribute to the aetiology of lymphoma, but partially inconsistent with the Th1/Th2-shift paradigm.

Occupational Exposure to Immunologically Active Agents and Risk for Lymphoma

Objectives: We evaluated whether occupational exposure to high molecular weight agents that are associated with asthma and that act predominantly through an immunoglobulin E (IgE)–dependent hypersensitivity mechanism is also associated with risk for specific lymphoma types.

Methods: The Spanish lymphoma case-control study includes 519 newly diagnosed cases of lymphoid neoplasms and 554 hospital controls ages 20 to 80 years. Lymphomas were histologically or cytologically confirmed and classified according to the WHO classification. Lifetime occupational exposure to seven high molecular weight agents such as latex was evaluated through an asthma-specific job-exposure matrix and validated by an industrial hygienist. Odds ratios (OR) and 95% confidence intervals (95% CI) were adjusted for age, sex, hospital, and occupational exposures.

Results: Subjects exposed to high molecular weight agents had an increased risk for Hodgkin's lymphoma (OR, 2.27; 95% CI, 0.93-5.50), particularly nodular sclerosis (OR, 3.22; 95% CI, 1.14-9.09). ORs did not increase with duration of exposure to these agents. Exposure to high molecular weight agents was not associated with risk of other B-cell lymphomas; for most specific subcategories of B-cell lymphoma, ORs were below unity. A slightly increased OR (95% CI) was seen for mycosis fungoides [1.60 (0.53-4.84)], although overall there was no increased risk for T-cell lymphomas.

Conclusions: Exposure to immunologically active agents among clinically immunocompetent subjects was associated with risk for Hodgkin's lymphoma.

Number of Siblings and Risk of Hodgkin's Lymphoma

Background: Epidemiologic evidence indicates that risk of Hodgkin's lymphoma (HL) in young adults is associated with correlates of delayed exposure to infection during childhood. In contrast, HL among children and older adults may be associated with earlier childhood infection. This study examines the associations of HL risk with having older or younger siblings. Methods: We conducted a case-control study in Sweden comparing 2,140 HL patients identified from the Swedish Cancer Register with 10,024 controls identified from national population registers. The Swedish Multi-Generation Register was used to link individuals to their parents and siblings. Results: Among young adults ages 15 to 39 years, the odds ratios (OR) associated with having one, two, and three or more older siblings, compared with none, were 0.96 [95% confidence interval (CI), 0.82-1.13], 0.88 (95% CI, 0.72-1.09), and 0.72 (95% CI, 0.55-0.93), respectively (P value for trend = 0.01). In contrast, number of older siblings was not associated with HL risk among children or older adults. Number of younger or total siblings, mother's age at birth, and father's occupation were not associated with HL at any age. The decreased risk of young-adult HL did not vary appreciably by age difference or sex of older siblings. Conclusions: Risk of HL was lower among young adults with multiple older but not younger siblings. Having older siblings is associated with earlier exposure to common childhood pathogens. Pediatric and older-adult HL were not associated with number of siblings, suggesting a different pathogenesis of disease in these age groups.

Population-based study of lymphoma in Germany: rationale, study design and first results

A multi-centre, population-based case-control study of lymphoma among adults was conducted in Germany from 1999-2003. The study comprised 700 incident cases (Hodgkin lymphomas and non Hodgkin's lymphoma, NHL) in the age range 18-80 years and 700 age-, sex- and area-matched controls obtained from population registries. Diagnosis was based on the REAL/WHO classification. Information on demographic characteristics, lifestyle, medical history and occupation was obtained by in-person interviews. Each participant was asked for a 24 ml blood sample. First results are focused on basic demographic characteristics, contact to animals, childhood diseases and vaccinations. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using conditional logistic regression. The ORs for lymphoma were decreased for exposure to sheep and goats (OR = 0.7; 95% CI = 0.5-0.9), for rabbits and hare (OR = 0.7; 95% CI = 0.5-0.9), measles infection (OR = 0.6; 95% CI = 0.5-0.9), Bordetella pertussis infection (OR = 0.7; 95% CI = 0.6-0.95), and tetanus vaccination (OR = 0.5; 95% CI = 0.3-0.9). Increased risk of lymphoma was associated with exposure to cattle (OR = 1.3; 95% CI = 1.03-1.7) and immunization for tuberculosis (OR = 1.5; 95% CI = 0.997-2.4). The results of this study are partly consistent with the hygiene hypothesis. The inconsistencies of some of the findings with an explanation by the Th1/Th2 paradigm, however, warrant further research and may indicate that broader explanatory concepts are needed.

Association between late age at infectious mononucleosis, Epstein-Barr virus antibodies, and ovarian cancer risk

We conducted two studies to evaluate the hypothesis that late age at first exposure to a common infectious agent such as Epstein-Barr virus (EBV) may be related to the risk of developing epithelial ovarian cancer. Because EBV more commonly results in infectious mononucleosis (IM) when primary infection occurs at a late age, we first assessed risk associated with age at IM in a population-based case-control study using unconditional logistic regression to estimate odds ratios and their 95% confidence intervals. Risk of ovarian cancer was 0.0, 0.9, 1.5, and 2.1 among women diagnosed with IM at < 15, 15-19, 20-24, and > 24 years, respectively, relative to women never diagnosed with IM (p for trend among women with IM = 0.02). In a second study, we examined EBV antibody titers among an independent sample of ovarian cancer cases and controls. Women with elevated IgG titers to viral capsid antigen, a marker of a relatively severe (and, conceivably, later) initial EBV infection, had a 5.3-fold (95% CI 1.5-18.4) increased risk of ovarian cancer. Together, these two studies provide some support for the hypothesis that late age at primary infection with a common agent (conceivably, EBV) may play a role in the etiology of ovarian cancer.

Sun exposure may protect against non-Hodgkin lymphoma: A case-control study

Ultraviolet radiation is a hypothesised risk factor for non-Hodgkin lymphoma (NHL) but no epidemiological study has examined this association using direct measures of sun exposure in individuals. Adults aged 20-74 years living in NSW and ACT, Australia, were the study population. Cases (704 of 829 invited to take part, 85%) were diagnosed January 2000 to August 2001. Controls (694 of 1,136 invited to take part, 61%) were randomly selected from state electoral rolls and frequency-matched to cases by age, sex and state of residence. A self-administered questionnaire and telephone interview measured outdoor hours on working and nonworking days and vacations at 10, 20, 30, 40, 50 and 60 years of age. Logistic regression models of NHL and sun exposure contained the 3 matching variables, ethnicity and sun sensitivity measures as covariates. Contrary to expectations, risk of NHL fell with increasing reported sun exposure hours. Relative to 1.0 for the lowest quarter of total sun exposure hours, the odds ratios (ORs) for successively higher quarters were 0.72 (95% CI 0.53-0.98), 0.66 (0.48-0.91) and 0.65 (0.46-0.91) (p(trend)=0.01). The association of sun exposure on nonworking days with NHL was stronger; OR for highest quarter 0.47 (0.34-0.66) (p(trend)=0.0001). Risk also fell with sun exposure on vacations; OR for highest quarter 0.60 (0.43-0.85) (p(trend)=0.003). These associations appeared strongest in women and in childhood. There was little evident trend in risk with exposure on working day. Our results provide strong statistical evidence for an inverse association between sun exposure and NHL. Increasing evidence that vitamin D may protect against cancer makes UV-mediated synthesis of vitamin D a plausible mechanism whereby sun exposure might protect against NHL.

Cancer incidence in adolescents and young adults in the United States, 1992-1997

PURPOSE

To examine cancer incidence patterns among adolescents and young adults in the United States.

METHODS

Cancer incidence data from 26 population-based central cancer registries for 1992-1997 were used. Individual cancers were grouped into specific diagnostic groups and subgroups using an integrated classification scheme. The integrated scheme was developed for this study and was based on the most commonly used schemes in population-based epidemiologic studies: Surveillance, Epidemiology, and End Results Program's site groups, International Classification of Childhood Cancer, and International Agency for Research on Cancer's Histological Groups for Comparative Studies. Percent distributions and age-specific incidence rates per million population were computed for adolescents (aged 15-19 years) and young adults (aged 20-24 years) by gender.

RESULTS

The data for 26,010 cancer cases were examined. Among 15-19-year-olds, the five most common cancers were Hodgkin's disease, leukemia, cancer in the brain and other nervous system, bone cancer, and non-Hodgkin's disease. Among 20-24-year-olds, the five most common cancers were Hodgkin's disease, testicular cancer, thyroid cancer, melanoma of the skin, and leukemia. The proportions and rates of the histologic subtypes for most of the common cancers changed with advancing age. For example, among 15-19-year-olds, acute lymphocytic leukemia accounted for approximately 60% of leukemias in males and 50% in females. Among 20-24-year-olds, however, the corresponding percentages of acute lymphocytic leukemia were 37% in males and 31% in females. For ovarian cancer, the germ cell tumor was the most common subtype (54.6% of all ovarian cancers) among 15-19-year-olds. In contrast, ovarian carcinoma was the predominant subtype (70.4%) among 20-24-year-olds. For both age groups, the incidence rates of nodular Hodgkin's disease, melanoma of the skin, and thyroid cancer were significantly greater in females than in males.

CONCLUSIONS

Cancer incidence patterns among adolescents and young adults are distinctive. In these age groups, a transition from predominantly pediatric histologic subtypes to adult subtypes was observed for Hodgkin's disease, leukemia, ovarian cancer, and soft tissue sarcoma. Gender differences were found for Hodgkin's disease, melanoma of the skin, and thyroid cancer.

Delayed infection, late tonsillectomy or adenoidectomy and adult leukaemia: a case-control study

In a population-based case-control study among adults in Italy, of 261 lymphoid and 313 myeloid leukaemias and 1718 controls, a later age at adenoidectomy and tonsillectomy (after age 10 years) increased considerably the risk of lymphocytic (but not myeloid) leukaemia (odds ratio 4.2, 95% confidence interval 1.1-16.2). We propose that late infection is a proliferative stimulus for B-cells.

Social class and risk of Hodgkin's disease in young-adult women in 1988-94

Hodgkin's disease (HD) risk in young adults has been associated with higher childhood social class. Although recent decades have witnessed increases in both young-adult HD incidence rates and the socioeconomic affluence reported to influence risk, social class risk factors have not been reexamined. For 204 cases and 254 controls aged 19-44 years from a population-based case-control study of HD diagnosed in 1988-94 in San Francisco area females, we evaluated social class predictors of HD overall and for subgroups defined by age and by ethnicity. HD was associated weakly with a few childhood social class markers but more strongly with combinations of these variables. Risk was higher for women with family-owned than rented childhood homes; for US-born women with single vs. shared bedrooms at age 11; and for women with 2+ births who were from smaller than larger childhood households. These patterns differed by age, with risk appearing to increase over the young-adult years for some factors and to decrease for others. In whites, risk was additionally associated with having a single childhood bedroom in larger households, and with tall adult height in women from smaller childhood households. In nonwhites, risk was higher for single bedrooms at age 11 in smaller childhood households, taller height and higher maternal education. Most study findings support the hypothesis that HD development in young adults follows protection from early exposure to other children. Variation in risk by age suggests differing etiologies across young adulthood, or the importance of birth cohort-appropriate social-class measures. Negative findings for previously reported risk factors may reflect their insufficient heterogeneity of exposure or their failure to measure cohort-relevant exposures in this population.