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

Mode of Delivery, Birth Characteristics, and Early-Onset Non-Hodgkin Lymphoma in a Population-Based Case-Control Study

BACKGROUND

The etiology of non-Hodgkin lymphoma (NHL) in children and in adolescents and young adults (AYA) is not well understood.

METHODS

We evaluated potential associations between mode of delivery, birth characteristics, and NHL risk in a population-based case-control study, which included 3,064 cases of NHL [490 with Burkitt lymphoma, 981 with diffuse large B-cell lymphoma (DLBCL), and 978 with T-cell NHL) diagnosed at the age of 0 to 37 years in California during 1988 to 2015 and 153,200 controls frequency matched on year of birth. Odds ratios (OR) and 95% confidence intervals (CI) were estimated from an unconditional multivariable logistic regression model that included year of birth and birth characteristics.

RESULTS

Individuals born via cesarean section had a decreased risk of pediatric Burkitt lymphoma (age 0-14 years; OR = 0.71, 95% CI: 0.51-0.99) and pediatric T-cell NHL (OR = 0.73, 95% CI: 0.55-0.97) compared with those born vaginally. Having a birth order of second (OR = 0.73, 95% CI: 0.57-0.93) or third or higher (OR = 0.76, 95% CI: 0.58-0.99) was associated with a lower risk of pediatric T-cell NHL compared with first-borns. AYA (age 15-37 years) with a heavier birthweight had an elevated risk of DLBCL (OR for each kg = 1.16, 95% CI: 1.00-1.35). Associations between other birth characteristics, including plurality, maternal age, maternal education, and NHL risk, also exhibited variations across subgroups based on age of diagnosis and histologic subtype.

CONCLUSIONS

These findings support a role of mode of delivery and birth characteristics in the etiology of early-onset NHL.

IMPACT

This study underscores the etiologic heterogeneity of early-onset NHL.

Impact of maternal reproductive factors on cancer risks of offspring: A systematic review and meta-analysis of cohort studies

Background

A number of studies have reported on associations between reproductive factors, such as delivery methods, number of birth and breastfeeding, and incidence of cancer in children, but systematic reviews addressing this issue to date have important limitations, and no reviews have addressed the impact of reproductive factors on cancer over the full life course of offspring.

Methods

We performed a comprehensive search in MEDLINE, and Embase up to January 2020 and Web of Science up to 2018 July, including cohort studies reporting the association between maternal reproductive factors of age at birth, birth order, number of births, delivery methods, and breastfeeding duration and cancer in children. Teams of two reviewers independently extracted data and assessed risk of bias. We conducted random effects meta-analyses to estimate summary relative estimates, calculated absolute differences between those with and without risk factors, and used the GRADE approach to evaluate the certainty of evidence.

Results

For most exposures and most cancers, we found no suggestion of a causal relation. We found low to very low certainty evidence of the following very small possible impact: higher maternal age at birth with adult multiple myeloma and lifetime uterine cervix cancer incidence; lower maternal age at birth with childhood overall cancer mortality (RR = 1.15, 95% CI = 1.01–1.30; AR/10,000 = 1, 95% CI = 0 to 2), adult leukemia and lifetime uterine cervix cancer incidence; higher birth order with adult melanoma, cervix uteri, corpus uteri, thyroid cancer incidence, lifetime lung, corpus uteri, prostate, testis, sarcoma, thyroid cancer incidence; larger number of birth with childhood brain (RR = 1.27, 95% CI = 1.06–1.52; AR/10,000 = 1, 95% CI = 0 to 2), leukemia (RR = 2.11, 95% CI = 1.62–2.75; AR/10,000 = 9, 95% CI = 5 to 14), lymphoma (RR = 4.66, 95% CI = 1.40–15.57; AR/10,000 = 11, 95% CI = 1 to 44) incidence, adult stomach, corpus uteri cancer incidence and lung cancer mortality, lifetime stomach, lung, uterine cervix, uterine corpus, multiple myeloma, testis cancer incidence; Caesarean delivery with childhood kidney cancer incidence (RR = 1.25, 95% CI = 1.01–1.55; AR/10,000 = 0, 95% CI = 0 to 1); and breastfeeding with adult colorectal cancer incidence.

Conclusion

Very small impacts existed between a number of reproductive factors and cancer incidence and mortality in children and the certainty of evidence was low to very low primarily due to observational design.

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.

Prediagnostic plasma concentrations of organochlorines and risk of B-cell non-Hodgkin lymphoma in envirogenomarkers: a nested case-control study

BACKGROUND

Evidence suggests a largely environmental component to non-Hodgkin's lymphoma (NHL). Persistent organic pollutants (POPs) including polychlorinated biphenyls (PCBs), DDE and HCB have been repeatedly implicated, but the literature is inconsistent and a causal relationship remains to be determined.

METHODS

The EnviroGenoMarkers study is nested within two prospective cohorts EPIC-Italy and the Northern Sweden Health and Disease Study. Six PCB congeners, DDE and HCB were measured in blood plasma samples provided at recruitment using gas-chromatography mass spectrometry. During 16 years follow-up 270 incident cases of B-cell NHL (including 76 cases of multiple myeloma) were diagnosed. Cases were matched to 270 healthy controls by centre, age, gender and date of blood collection. Cases were categorised into ordered quartiles of exposure for each POP based on the distribution of exposure in the control population. Logistic regression was applied to assess the association with risk, multivariate and stratified analyses were performed to identify confounders or effect modifiers.

RESULTS

The exposures displayed a strong degree of correlation, particularly amongst those PCBs with similar degrees of chlorination. There was no significant difference (p < 0.05) in median exposure levels between cases and controls for any of the investigated exposures. However under a multivariate model PCB138, PCB153, HCB and DDE displayed significant inverse trends (Wald test p-value <0.05). Under stratified analyses these were determined to be driven by males and by the Diffuse Large B-Cell Lymphoma subtype. When considering those in the highest levels of exposure (>90^th percentile) the association was null for all POPs CONCLUSION: We report no evidence that a higher body burden of PCBs, DDE or HCB increased the risk of subsequent NHL diagnosis. Significantly inverse associations were noted for males with a number of the investigated POPs. We hypothesize these unexpected relationships may relate to the subtype composition of our population, effect modification by BMI or other unmeasured confounding. This study provides no additional support for the previously observed role of PCBs, DDE and HCB as risk factors for NHL.

Environmental, maternal, and reproductive risk factors for childhood acute lymphoblastic leukemia in Egypt: a case-control study

BACKGROUND

Acute lymphocytic leukemia (ALL) is the most common pediatric cancer. The exact cause is not known in most cases, but past epidemiological research has suggested a number of potential risk factors. This study evaluated associations between environmental and parental factors and the risk for ALL in Egyptian children to gain insight into risk factors in this developing country.

METHODS

We conducted a case-control design from May 2009 to February 2012. Cases were recruited from Children's Cancer Hospital, Egypt (CCHE). Healthy controls were randomly selected from the general population to frequency-match the cumulative group of cases by sex, age groups (<1; 1 - 5; >5 - 10; >10 years) and region of residence (Cairo metropolitan region, Nile Delta region (North), and Upper Egypt (South)). Mothers provided answers to an administered questionnaire about their environmental exposures and health history including those of the father. Odds ratios (ORs) and 95 % confidence intervals (CI) were calculated using logistic regression with adjustment for covariates.

RESULTS

Two hundred ninety nine ALL cases and 351 population-based controls frequency-matched for age group, gender and location were recruited. The risk of ALL was increased with the mother's use of medications for ovulation induction (ORadj = 2.5, 95 % CI =1.2 -5.1) and to a lesser extend with her age (ORadj = 1.8, 95 % CI = 1.1 - 2.8, for mothers ≥ 30 years old). Delivering the child by Cesarean section, was also associated with increased risk (ORadj = 2.01, 95 % CI =1.24-2.81).

CONCLUSIONS

In Egypt, the risk for childhood ALL appears to be associated with older maternal age, and certain maternal reproductive factors.

Birth order and risk of hepatocellular carcinoma in chronic carriers of hepatitis B virus: a case-control study in The Gambia

BACKGROUND & AIMS

Early age at infection with Hepatitis B virus (HBV) increases the risk of chronic infection. Moreover, early HBV infection may further independently increase the risk of hepatocellular carcinoma (HCC) beyond its effect on chronicity.

METHODS

The distribution of birth order, a proxy for mode and timing of HBV transmission, was compared in The Gambia between hepatitis B surface antigen (HBsAg)-positive HCC cases recruited from hospitals (n = 72) and two HBsAg-positive control groups without HCC: population-based controls from a community HBV screening (n = 392) and hospital-based controls (n = 63).

RESULTS

HCC risk decreased with increasing birth order in the population-based case-control analysis. Using first birth order as the reference, the odds ratios were 0.52 (95% CI: 0.20-1.36), 0.52 (0.17-1.56), 0.57 (0.16-2.05) and 0.14 (0.03-0.64) for second, third, fourth and greater than fourth birth order respectively (P = 0.01). A similar inverse association was observed in the hospital-based case-control comparison (P = 0.04).

CONCLUSIONS

Compared to controls, HCC cases had earlier birth order, a proxy for young maternal age and maternal HBV viraemia at birth. This finding suggests that in chronic HBV carriers perinatal mother-to-infant transmission may increase HCC risk more than horizontal transmission. Providing HBV vaccine within 24 h of birth to interrupt perinatal transmission might reduce the incidence of HCC in The Gambia.

Common immune-related exposures/conditions and risk of non-Hodgkin lymphoma: a case-control study of disease-discordant twin pairs

We evaluated the association between common immune system-altering experiences and non-Hodgkin lymphoma (NHL) risk using a case-control study of 162 like-sex twin pairs discordant for NHL, identified from the International Twin Study. Information on medical history and evidence of childhood exposure to microbes was obtained by questionnaire from 1998 to 2002. Conditional logistic regression was used to estimate odds ratios and 95% confidence intervals. Intra-twin-pair agreement between twins on individual exposures was high (76%-97%). A negative association between NHL and seasonal hay fever (odds ratio (OR) = 0.28, 95% confidence interval (CI): 0.10, 0.75) and certain allergies (OR = 0.29, 95% CI: 0.13, 0.68) was observed. The number of atopic diseases was negatively associated with NHL (P for trend = 0.0003). A history of infectious mononucleosis was negatively associated with NHL risk (OR = 0.35, 95% CI: 0.14, 0.90). NHL risk was associated with more frequent childhood exposure to microbes during early life (P for trend = 0.04). No differences in association by NHL subtype were observed, although statistical power for these comparisons was low. These observations support the hypothesis that immune-related exposures, especially atopy, are associated with decreased NHL risk. Use of the within-twin-pair study design mitigates confounding by genome, family structure, and unmeasured characteristics of early childhood factors.

Early-life hygiene-related factors affect risk of central nervous system demyelination and asthma differentially

The increasing prevalence of immune-related diseases, including multiple sclerosis, may be partly explained by reduced microbial burden during childhood. Within a multi-centre case-control study population, we examined: (i) the co-morbid immune diseases profile of adults with a first clinical diagnosis of central nervous system demyelination (FCD) and (ii) sibship structure in relation to an autoimmune (FCD) and an allergic (asthma) disease. FCD cases (n = 282) were aged 18-59 years; controls (n = 558) were matched on age, sex and region. Measures include: history of doctor-diagnosed asthma; sibling profile (number; dates of birth); and regular childcare attendance. FCD cases did not differ from controls with regard to personal or family history of allergy, but had a greater likelihood of chronic fatigue syndrome [odds ratio (OR) = 3·11; 95% confidence interval (CI) 1·11, 8·71]. Having any younger siblings showed reduced odds of FCD (OR = 0·68; 95% CI: 0·49, 0·95) but not asthma (OR = 1·47; 95% CI: 0·91, 2·38). In contrast, an increasing number of older siblings was associated with reduced risk of asthma (P trend = 0·04) but not FCD (P trend = 0·66). Allergies were not over-represented among people presenting with FCD. Sibship characteristics influence both FCD and asthma risk but the underlying mechanisms differ, possibly due to the timing of the putative 'sibling effect'.

Occupational exposure and risk of central nervous system demyelination

Inconsistent evidence exists regarding the association between work-related factors and risk of multiple sclerosis (MS). We examined the association between occupational exposures and risk of a first clinical diagnosis of central nervous system demyelination (FCD), which is strongly associated with progression to MS, in a matched case-control study of 276 FCD cases and 538 controls conducted in Australia (2003-2006). Using a personal residence and work calendar, information on occupational history and exposure to chemicals and animals was collected through face-to-face interviews. Few case-control differences were noted. Fewer cases had worked as professionals (≥6 years) than controls (adjusted odds ratio (AOR) = 0.60, 95% confidence interval (CI): 0.37, 0.96). After further adjustment for number of children, cases were more likely to have ever been exposed to livestock than controls (AOR = 1.54, 95% CI: 1.03, 2.29). Among women, there was an increase in FCD risk associated with 10 or more years of exposure to livestock (AOR = 2.78, 95% CI: 1.22, 6.33) or 6 or more years of farming (AOR = 2.00, 95% CI: 1.23, 3.25; also adjusted for number of children). Similar findings were not evident among men. Thus, farming and exposure to livestock may be important factors in the development of FCD among women, with this finding further revealed after the confounding effect of parity or number of children is considered.

A case-control study of medium-term exposure to ambient nitrogen dioxide pollution and hospitalization for stroke

Background

There are several plausible mechanisms whereby either short or long term exposure to pollution can increase the risk of stroke. Over the last decade, several studies have reported associations between short-term (day-to-day) increases in ambient air pollution and stroke. The findings from a smaller number of studies that have looked at long-term exposure to air pollution and stroke have been mixed. Most of these epidemiological studies have assigned exposure to air pollution based on place of residence, but these assignments are typically based on relatively coarse spatial resolutions. To date, few studies have evaluated medium-term exposures (i.e, exposures over the past season or year). To address this research gap, we evaluated associations between highly spatially resolved estimates of ambient nitrogen dioxide (NO₂), a marker of traffic pollution, and emergency department visits for stroke in Edmonton, Canada.

Methods

This was a case-control study with cases defined as those who presented to an Edmonton area hospital emergency department between 2007 and 2009 with an acute ischemic stroke, hemorrhagic stroke, or transient ischemic attack. Controls were patients who presented to the same emergency departments for lacerations, sprains, or strains. A land-use regression model provided estimates of NO₂ that were assigned to the place of residence. Logistic regression methods were used to estimate odds ratios for stroke in relation to an increase in the interquartile range of NO₂ (5 ppb), adjusted for age, sex, meteorological variables, and neighborhood effects.

Results

The study included 4,696 stroke (cases) and 37,723 injury patients (controls). For all strokes combined, there was no association with NO_2. Namely, the odds ratio associated with an interquartile increase in NO₂ was 1.01 (95% confidence interval {CI}: 0.94-1.08). No associations were evident for any of the stroke subtypes examined.

Conclusion

When combined with our earlier work in Edmonton, our findings suggest that day-to-day fluctuations in air pollution increase the risk of ischemic stroke during the summer season, while medium term exposures are unrelated to stroke risk. The findings for medium term exposure should be interpreted cautiously due to limited individual-level risk factor data.

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.

Epidemiology, epigenetics and the 'Gloomy Prospect': embracing randomness in population health research and practice

Epidemiologists aim to identify modifiable causes of disease, this often being a prerequisite for the application of epidemiological findings in public health programmes, health service planning and clinical medicine. Despite successes in identifying causes, it is often claimed that there are missing additional causes for even reasonably well-understood conditions such as lung cancer and coronary heart disease. Several lines of evidence suggest that largely chance events, from the biographical down to the sub-cellular, contribute an important stochastic element to disease risk that is not epidemiologically tractable at the individual level. Epigenetic influences provide a fashionable contemporary explanation for such seemingly random processes. Chance events-such as a particular lifelong smoker living unharmed to 100 years-are averaged out at the group level. As a consequence population-level differences (for example, secular trends or differences between administrative areas) can be entirely explicable by causal factors that appear to account for only a small proportion of individual-level risk. In public health terms, a modifiable cause of the large majority of cases of a disease may have been identified, with a wild goose chase continuing in an attempt to discipline the random nature of the world with respect to which particular individuals will succumb. The quest for personalized medicine is a contemporary manifestation of this dream. An evolutionary explanation of why randomness exists in the development of organisms has long been articulated, in terms of offering a survival advantage in changing environments. Further, the basic notion that what is near-random at one level may be almost entirely predictable at a higher level is an emergent property of many systems, from particle physics to the social sciences. These considerations suggest that epidemiological approaches will remain fruitful as we enter the decade of the epigenome.

Reproductive factors and lymphoid neoplasms in Europe: findings from the EpiLymph case-control study

BACKGROUND

The study of lymphomagenesis has rarely focused on hormonal factors. Higher incidence rates are observed for many lymphoma subtypes in men compared with women suggesting an underlying association. Our goal was to investigate the association between reproductive factors and lymphomas.

METHODS

The Epilymph study is a multicenter case-control study carried out in six European countries from 1998 to 2004. Female cases of mature T-cell neoplasms (n = 52), Hodgkin lymphoma (n = 147), and mature B-cell neoplasms (n = 795), including its common subtypes, and their respective controls (n = 1,141) frequency matched by age, gender, and center were considered.

RESULTS

An odds reduction of 29% (95% CI -46 to -6%) was observed for mature T-cell neoplasms for each child increase among parous women and of 13% (95% CI -19 to -7%) for mature B-cell neoplasms; while no association was observed for Hodgkin lymphoma. By B-cell neoplasm subtypes, these associations were found for chronic lymphocytic leukemia/small lymphocytic lymphoma (-21%, 95% CI -31 to -9%) and diffuse large B-cell lymphoma (DLBCL; -14%; 95% CI -23 to -3%). Overall, no associations were observed with age at first and last pregnancy, and ever use of hormonal contraceptives and lymphoma. Higher odds ratios for a short-term use of hormonal contraceptives (<5 years), but not for a long-term use, were observed for mature B-cell neoplasms, DLBCL, and follicular lymphoma compared with never use.

CONCLUSION

These data support the hypothesis that increased parity confers a protective effect against lymphoma. Less clearly, our results also indicate that hormonal contraceptives could play a role.

Lymphoid malignancies in U.S. Asians: incidence rate differences by birthplace and acculturation

BACKGROUND

Malignancies of the lymphoid cells, including non-Hodgkin lymphomas (NHL), HL, and multiple myeloma, occur at much lower rates in Asians than other racial/ethnic groups in the United States. It remains unclear whether these deficits are explained by genetic or environmental factors. To better understand environmental contributions, we examined incidence patterns of lymphoid malignancies among populations characterized by ethnicity, birthplace, and residential neighborhood socioeconomic status (SES) and ethnic enclave status.

METHODS

We obtained data about all Asian patients diagnosed with lymphoid malignancies between 1988 and 2004 from the California Cancer Registry and neighborhood characteristics from U.S. Census data.

RESULTS

Although incidence rates of most lymphoid malignancies were lower among Asian than white populations, only follicular lymphoma (FL), chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), and nodular sclerosis (NS) HL rates were statistically significantly lower among foreign-born than U.S.-born Asians with incidence rate ratios ranging from 0.34 to 0.87. Rates of CLL/SLL and NS HL were also lower among Asian women living in ethnic enclaves or lower SES neighborhoods than those living elsewhere.

CONCLUSIONS

These observations support strong roles of environmental factors in the causation of FL, CLL/SLL, and NS HL.

IMPACT

Studying specific lymphoid malignancies in U.S. Asians may provide valuable insight toward understanding their environmental causes.