Meat intake and risk of non-Hodgkin lymphoma

Dietary intake of animal-based products and likelihood of follicular lymphoma and survival: A population-based family case-control study

Background

The association between dietary intake of foods of animal origin and follicular lymphoma (FL) risk and survival is uncertain. In this study, we examined the relationship between dietary intake of dairy foods and fats, meat, fish and seafoods, and the likelihood of FL and survival.

Methods

We conducted a population-based family case-control study in Australia between 2011 and 2016 and included 710 cases, 303 siblings and 186 spouse/partner controls. We assessed dietary intake of animal products prior to diagnosis (the year before last) using a structured food frequency questionnaire and followed-up cases over a median of 6.9 years using record linkage to national death data. We examined associations with the likelihood of FL using logistic regression and used Cox regression to assess association with all-cause and FL-specific mortality among cases.

Results

We observed an increased likelihood of FL with increasing daily quantity of oily fish consumption in the year before last (highest category OR = 1.96, CI = 1.02-3.77; p-trend 0.06) among cases and sibling controls, but no associations with spouse/partner controls. We found no association between the likelihood of FL and the consumption of other types of fish or seafood, meats or dairy foods and fats. In FL cases, we found no association between meat or oily fish intake and all-cause or FL-specific mortality.

Conclusion

Our study showed suggestive evidence of a positive association between oily fish intake and the likelihood of FL, but findings varied by control type. Further investigation of the potential role of environmental contaminants in oily fish on FL etiology is warranted.

Etiology of non-Hodgkin lymphoma: A review from epidemiologic studies

Non-Hodgkin lymphoma (NHL) contributes to significant cancer burden and mortality globally. In recent years, much insight into the causes of NHL has been gained by evaluating global differences through international collaboration and data pooling. NHL comprises different subtypes that are known to behave differently, exhibit different prognoses, and start in distinct cell types (B-cell, T-cell, and NK-cell, predominantly), and there is increasing evidence that NHL subtypes have different etiologies. Classification of NHL can be complex, with varying subtype frequencies, and is a consideration when evaluating geographic differences. Because of this, international pooling of well-executed epidemiologic studies has conferred power to evaluate NHL by subtype and confidence with minimal misclassification. Given the decreasing burden in some regions while cases rise in Asia, and especially China, this report focuses on a review of the established etiology of NHL from the epidemiologic literature in recent decades, highlighting work from China. Topics covered include demographic patterns and genetic determinants including family history of NHL, as well as infection and immunosuppression, lifestyle, environment, and certain occupational exposures contributing to increased disease risk.

Levels of evidence for the association between different food groups/items consumption and the risk of various cancer sites: an umbrella review

This study aimed to determine the level of evidence on the association between food groups/items consumption and the risk of different cancer sites from the meta-analyses/pooled analyses of observational studies. A systematic search was executed in Scopus, PubMed/MEDLINE, and Web of Science. The criteria from the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) Expert Report were adopted for evidence grading. In summary, there was convincing evidence for the association between fibre intake and decreased risk of colon and breast cancer. Also, consumption of dairy products, milk, fruits, and fibre was associated with a probable decreased risk of breast cancer. Consumption of whole grains, dairy products, milk, fruits, vegetables, and fibre had a probable inverse association with the incidence risk of gastrointestinal tract cancers. More qualified studies are needed to find reliable findings on the association between various food groups/items consumption and the risk of different cancer sites.

Investigation of the incidence trend of follicular lymphoma from 2008 to 2017 in Taiwan and the United States using population-based data

Background

The incidence of follicular lymphoma (FL) in Taiwan has not been well investigated since its inclusion as a histological subtype in the Taiwan Cancer Registry in 2008. The purpose of this study was to describe the incidence patterns of FL in Taiwan and compare the trends with those in other racial groups in the United States.

Materials and methods

We conducted an epidemiological study using population-based data from the Taiwan Cancer Registry, Ministry of Health and Welfare, and the 18 Surveillance, Epidemiology, and End Results (SEER) registries to evaluate the FL incidence from 2008 to 2017. We calculated the annual percent change (APC) to describe the trends in the incidence of FL in subpopulations defined by race and sex over time.

Results

The annual age-adjusted incidence rate of FL in Taiwan increased significantly from 0.59 per 100,000 persons in 2008 to 0.82 per 100,000 persons in 2017, with an APC of 3.2. By contrast, the incidence rate in whites in the United States during the same period decreased from 3.42 to 2.74 per 100,000 persons, with an APC of −2.1. We found no significant change for the blacks (APC, −1.5%), Hispanics (APC, −0.7%), and Asians or Pacific Islanders (APC, +0.7%). The temporal trend was similar between the males and females. The relative frequency of FL among the incident non-Hodgkin lymphoma (NHL) cases also increased significantly in Taiwan from 7.64% in 2008 to 11.11% in 2017 (APC = 3.8). The relative frequency of FL among the incident NHL cases in the whites decreased from 2008 to 2012 (APC, −3.8%) and then stabilized after 2012 (APC, −0.2%). By contrast, little change in relative frequency of FL among the incident NHL cases was observed in the blacks, Hispanics, and APIs between 2008 and 2017.

Conclusion

We found increases in the incidence of FL and the relative frequency of FL among the incident NHL cases in both males and females in Taiwan from 2008 to 2017. The FL incidence rates were unchanged for all races and sex groups in the United States, except for the decreases in the whites.

The Dietary Inflammatory Index and Chronic Lymphocytic Leukaemia in the MCC Spain Study

Chronic inflammation plays a role in the development of chronic lymphocytic leukaemia (CLL), and diet might modulate chronic inflammation. This study aims to evaluate the association between the dietary inflammatory index (DII®) and CLL. A total of 366 CLL cases and 1643 controls of the Spanish multicase-control (MCC) Spain study were included. The inflammatory potential of the diet was assessed using the energy-adjusted dietary inflammatory index (E-DII) based on 30 items from a validated semi-quantitative food frequency questionnaire. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression models controlling for potential confounders. Overall, a modest, non-statistically significant, positive association was observed between CLL and E-DII scores (OR for a one-unit increase in E-DII: 1.05 (CI 95%: 0.99, 1.12), p-value = 0.09 and by tertiles: ORT2vsT1: 1.20 (CI 95%: 0.90, 1.59); OR T3vsT1: 1.21 (CI 95%: 0.90, 1.62), p trend = 0.21). These results were independent from disease severity (p-het: 0.70), time from diagnosis (p-het: 0.67) and CLL treatment received (p-het: 0.56). No interactions were detected. In conclusion, the consumption of a diet with high pro-inflammatory components was not significantly associated with CLL. Changes towards a more pro-inflammatory dietary pattern in younger generations not included here warrant future research.

Meat, fish, dairy products and risk of hematological malignancies in adults - a systematic review and meta-analysis of prospective studies

This systematic review and meta-analysis of cohort studies examine the association of meat, fish, and dairy product consumption with the risk of hematological neoplasms in adults. Thirteen studies encompassing 1,480,986 participants and 10,442 incident cases were included. Red or processed meat consumption was not associated with the risk of leukemia, acute myeloid leukemia, non-Hodgkin lymphoma (NHL) and small lymphocytic lymphoma/chronic lymphocytic leukemia (CLL/SLL). Poultry consumption did not seem to affect the risk of leukemia, NHL, CLL/SLL, and multiple myeloma (MM). Fish consumption was not associated with leukemia, NHL, CLL/SLL, and MM risk. Interestingly though, fish consumption was positively associated with myeloid leukemia risk (pooled RR = 1.74, 95% CI: 1.22-2.47, random effects, highest vs. lowest category). Milk and dairy product consumption was not associated with NHL and leukemia risk. In conclusion, methodologically strict prospective studies are mandatory, in order to extract reliable conclusions concerning the role of these dietary factors in hematological malignancies.

Adherence to the Western, Prudent, and Mediterranean dietary patterns and chronic lymphocytic leukemia in the MCC-Spain study

Diet is a modifiable risk factor for several neoplasms but evidence for chronic lymphocytic leukemia (CLL) is sparse. Previous studies examining the association between single-food items and CLL risk have yielded mixed results, while few studies have been conducted on overall diet, reporting inconclusive findings. This study aimed to evaluate the association between adherence to three dietary patterns and CLL in the multicase-control study (MCC-Spain) study. Anthropometric, sociodemographic, medical and dietary information was collected for 369 CLL cases and 1605 controls. Three validated dietary patterns, Western, Prudent and Mediterranean, were reconstructed in the MCC-Spain data. The association between adherence to each dietary pattern and CLL was assessed, overall and by Rai stage, using mixed logistic regression models adjusted for potential confounders. High adherence to a Western dietary pattern (i.e. high intake of high-fat dairy products, processed meat, refined grains, sweets, caloric drinks, and convenience food) was associated with CLL [ORQ4 vs. Q1=1.63 (95%CI 1.11; 2.39); P-trend=0.02; OR 1-SD increase=1.19 (95%CI: 1.03; 1.37)], independently of Rai stages. No differences in the association were observed according to sex, Body Mass Index, energy intake, tobacco, physical activity, working on a farm, or family history of hematologic malignancies. No associations were observed for Mediterranean and Prudent dietary patterns and CLL. This study provides the first evidence for an association between a Western dietary pattern and CLL, suggesting that a proportion of CLL cases could be prevented by modifying dietary habits. Further research, especially with a prospective design, is warranted to confirm these findings.

Dietary fat intake and risk of non-Hodgkin lymphoma in 2 large prospective cohorts

Background: Dietary fat intake may contribute to non-Hodgkin lymphoma (NHL) pathogenesis by influencing carcinogen exposure or through immune modulation.Objective: We aimed to evaluate NHL risk associated with total and specific dietary fat intake.Design: We evaluated associations within the Nurses' Health Study (NHS) (n = 88,598) and the Health Professionals Follow-Up Study (HPFS) (n = 47,531) using repeated validated dietary assessments. We confirmed 1802 incident NHL diagnoses through 2010. Using multivariable Cox proportional hazards models, we estimated hazard ratios (HRs) for all NHL and common subtypes associated with a 1-SD increase in cumulative mean intakes of total, animal, saturated, trans, and vegetable fats and marine fatty acids. We pooled sex-specific HRs using random-effects meta-analysis.Results: Over 24-30 y of follow-up, neither total nor specific dietary fats were significantly associated with NHL risk overall. Higher total, animal, and saturated fat intakes were positively associated with the risk of the chronic lymphocytic leukemia/small lymphocytic lymphoma subtype among women only (253 cases; P-trend ≤ 0.05), driven by strong associations during 1980-1994. From baseline through 1994, among women and men combined, total fat intake was borderline-significantly positively associated with NHL overall (pooled HR per SD: 1.13; 95% CI: 0.99, 1.29) and was significantly associated with diffuse large B cell lymphoma (pooled HR per SD: 1.47; 95% CI: 1.06, 2.05), with similar trends for animal and saturated fat intake. For women only, trans fat was significantly positively associated with all NHL. In contrast, during 1994-2010, there was little evidence for associations of dietary fat intake with NHL overall or by subtype.Conclusion: Previous observations of an increased risk of NHL associated with intakes of total, animal, saturated, and trans fat with 14 y of follow-up did not persist with longer follow-up.

Dietary Fat Consumption and Non-Hodgkin's Lymphoma Risk: A Meta-analysis

OBJECTIVE

Many studies suggest that high-fat diets are linked to the etiology of non-Hodgkin's lymphoma (NHL). However, the findings are inconsistent and therefore the association between fat and non-Hodgkin's lymphoma remains unclear. In this study, we aim to quantitatively assess the association between fat consumption and the risk for NHL.

METHODS

We reviewed 221 published cohort and case-control studies that reported relative risk (RRs) and corresponding 95% confidence intervals (CIs) of NHL and fat intake using PubMed, Cochrane, EMBASE, and Google Scholar databases. A random-effects model computed summary risk estimates.

RESULTS

Based on our literature search, 10 of 221 studies (two cohort and eight case-control studies) were relevant to this meta-analysis. There was a significant association between total fat consumption and increased risk of NHL (RR = 1.26; 95% CI: 1.12-1.42); in addition, subgroup analysis showed a significant correlation with diffuse large B-cell lymphoma (RR = 1.41; 95% CI: 1.08-1.84) but not with follicular lymphoma (RR = 1.21; 95% CI: 0.97-1.52), small lymphocytic lymphoma/chronic lymphocytic leukemia (RR = 0.91; 95% CI: 0.68-1.23), nor with T cell lymphoma (RR = 1.12; 95% CI: 0.60-2.09). The funnel plot revealed no evidence for publication bias.

CONCLUSION

Total fat consumption, particularly animal fat, increases the risk for NHL.

Non-Hodgkin lymphoma in the developing world: review of 4539 cases from the International Non-Hodgkin Lymphoma Classification Project

The distribution of non-Hodgkin lymphoma subtypes varies around the world, but a large systematic comparative study has never been done. In this study, we evaluated the clinical features and relative frequencies of non-Hodgkin lymphoma subtypes in five developing regions of the world and compared the findings to the developed world. Five expert hematopathologists classified 4848 consecutive cases of lymphoma from 26 centers in 24 countries using the World Health Organization classification, and 4539 (93.6%) were confirmed to be non-Hodgkin lymphoma, with a significantly greater number of males than females in the developing regions compared to the developed world (P<0.05). The median age at diagnosis was significantly lower for both low- and high-grade B-cell lymphoma in the developing regions. The developing regions had a significantly lower frequency of B-cell lymphoma (86.6%) and a higher frequency of T- and natural killer-cell lymphoma (13.4%) compared to the developed world (90.7% and 9.3%, respectively). Also, the developing regions had significantly more cases of high-grade B-cell lymphoma (59.6%) and fewer cases of low-grade B-cell lymphoma (22.7%) compared to the developed world (39.2% and 32.7%, respectively). Among the B-cell lymphomas, diffuse large B-cell lymphoma was the most common subtype (42.5%) in the developing regions. Burkitt lymphoma (2.2%), precursor B- and T-lymphoblastic leukemia/lymphoma (1.1% and 2.9%, respectively) and extranodal natural killer/T-cell lymphoma (2.2%) were also significantly increased in the developing regions. These findings suggest that differences in etiologic and host risk factors are likely responsible, and more detailed epidemiological studies are needed to better understand these differences.

Meat intake and non-Hodgkin lymphoma: a meta-analysis of observational studies

PURPOSE

High intake of meat has been inconsistently associated with increased risk of non-Hodgkin lymphoma (NHL). We carried out a meta-analysis to summarize the evidence of published observational studies reporting association between red meat and processed meat intake and NHL risk.

METHODS

Analytical studies reporting relative risks with 95 % confidence intervals (95 % CI) for the association between intake of red and/or processed meat and NHL or major histological subtypes were eligible. We conducted random-effects meta-analysis comparing lowest and highest intake categories and dose-response meta-analysis when risk estimates and intake levels were available for more than three exposure classes.

RESULTS

Fourteen studies (four cohort and ten case-control) were included in the meta-analysis, involving a total of 10,121 NHL cases. The overall relative risks of NHL for the highest versus the lowest category of consumption were 1.14 (95 % CI 1.03, 1.26) for red meat and 1.06 (95 % CI 0.98, 1.15) for processed meat. Significant associations were present when the analysis was restricted to case-control studies but not when restricted to cohort studies. No significant associations were found for major NHL etiological subtypes. Dose-response meta-analysis could be based only on eight studies that provided sufficient data, and compared to no meat consumption, the overall NHL relative risk increased nonlinearly with increased daily intake of red meat.

CONCLUSION

The observed positive association between red meat consumption and NHL is mainly supported by the effect estimates coming from case-control studies and is affected by multiple sources of heterogeneity. This meta-analysis provided mixed and inconclusive evidences on the supposed relationship between red and processed meat consumption and NHL.

Non-Hodgkin lymphoma in Southern Africa: review of 487 cases from The International Non-Hodgkin Lymphoma Classification Project

Comparative data on the distribution of non-Hodgkin lymphoma (NHL) subtypes in Southern Africa (SAF) is scarce. In this study, five expert haematopathologists classified 487 consecutive cases of NHL from SAF using the World Health Organization classification, and compared the results to North America (NA) and Western Europe (WEU). Southern Africa had a significantly lower proportion of low-grade (LG) B-NHL (34·3%) and a higher proportion of high-grade (HG) B-NHL (51·5%) compared to WEU (54·5% and 36·4%) and NA (56·1% and 34·3%). High-grade Burkitt-like lymphoma was significantly more common in SAF (8·2%) than in WEU (2·4%) and NA (2·5%), most likely due to human immunodeficiency virus infection. When SAF patients were divided by race, whites had a significantly higher frequency of LG B-NHL (60·4%) and a lower frequency of HG B-NHL (32·7%) compared to blacks (22·5% and 62·6%), whereas the other races were intermediate. Whites and other races had a significantly higher frequency of follicular lymphoma and a lower frequency of Burkitt-like lymphoma compared to blacks. The median ages of whites with LG B-NHL, HG B-NHL and T-NHL (64, 56 and 67 years) were significantly higher than those of blacks (55, 41 and 34 years). Epidemiological studies are needed to better understand these differences.

Relative frequency of non-Hodgkin lymphoma subtypes in selected centres in North Africa, the middle east and India: a review of 971 cases

Comparative data regarding the distribution of non-Hodgkin lymphoma (NHL) subtypes in North Africa, the Middle East and India (NAF/ME/IN) is scarce in the literature. In this study, we evaluated the relative frequencies of NHL subtypes in this region. Five expert haematopathologists classified 971 consecutive cases of newly-diagnosed NHL from five countries in NAF/ME/IN. After review, 890 cases (91·7%) were confirmed to be NHL and compared to 399 cases from North America (NA). The male-to-female ratio was significantly higher in NAF/ME/IN (1·8) compared to NA (1·1; P< 0·05). The median ages of patients with low-grade (LG) and high-grade (HG) B-NHL in NAF/ME/IN (56 and 52 years, respectively) were significantly lower than in NA (64 and 68 years, respectively). In NAF/ME/IN, a significantly lower proportion of LG B-NHL (28·4%) and a higher proportion of HG B-NHL (58·4%) were found compared to NA (56·1% and 34·3%, respectively). Diffuse large B-cell lymphoma was more common in NAF/ME/IN (49·4%) compared to NA (29·3%), whereas follicular lymphoma was less common in NAF/ME/IN (12·4%) than in NA (33·6%). In conclusion, we found significant differences in NHL subtypes and clinical features between NAF/ME/IN and NA. Epidemiological studies are needed to better understand the pathobiology of these differences.

Non-Hodgkin lymphoma in the Far East: review of 730 cases from the international non-Hodgkin lymphoma classification project

Large and systematic studies of non-Hodgkin lymphoma (NHL) in the Far East (FE) with good comparative data are scarce in the literature. In this study, five expert hematopathologists classified 730 consecutive cases of newly-diagnosed NHL from four sites in the FE (excluding Japan) using the World Health Organization classification. The results were compared to 399 cases from North America (NA). We found a significantly higher male to female ratio in the FE compared to NA (1.7 versus 1.1; p < 0.05). The median ages of patients with low-grade (LG) and high-grade (HG) B-NHL in the FE (58 and 51 years, respectively) were significantly lower than in NA (64 and 68 years, respectively). The FE had a significantly lower relative frequency of B-NHL and a higher frequency of T-NHL (82 vs. 18 %) compared to NA (90.5 vs. 9.5 %). Among mature B cell lymphomas, the FE had a significantly higher relative frequency of HG B-NHL (54.8 %) and a lower frequency of LG B-NHL (27.2 %) than NA (34.3 and 56.1 %, respectively). Diffuse large B cell lymphoma was more common in the FE (49.4 %) compared to NA (29.3 %), whereas the relative frequency of follicular lymphoma was lower in the FE (9.4 %) compared to NA (33.6 %). Among T-NHL, nasal NK/T cell NHL was more frequent in the FE (5.2 %) compared to NA (0 %). Peripheral T cell lymphoma was also more common in the FE (9.1 %) than in NA (5.3 %). Further epidemiologic studies are needed to better understand the pathobiology of these differences.

Red and Processed Meat Consumption Increases Risk for Non-Hodgkin Lymphoma: A PRISMA-Compliant Meta-Analysis of Observational Studies

The association between consumption of red and processed meat and non-Hodgkin lymphoma (NHL) remains unclear. We performed a meta-analysis of the published observational studies to explore this relationship.We searched databases in MEDLINE and EMBASE to identify observational studies which evaluated the association between consumption of red and processed meat and risk of NHL. Quality of included studies was evaluated using Newcastle-Ottawa Quality Assessment Scale (NOS). Random-effects models were used to calculate summary relative risk (SRR) and the corresponding 95% confidence interval (CI).We identified a total of 16 case-control and 4 prospective cohort studies, including 15,189 subjects with NHL. The SRR of NHL comparing the highest and lowest categories were 1.32 (95% CI: 1.12-1.55) for red meat and 1.17 (95% CI: 1.07-1.29) for processed meat intake. Stratified analysis indicated that a statistically significant risk association between consumption of red and processed meat and NHL risk was observed in case-control studies, but not in cohort studies. The SRR was 1.11 (95% CI: 1.04-1.18) for per 100 g/day increment in red meat intake and 1.28 (95% CI: 1.08-1.53) for per 50 g/day increment in processed meat intake. There was evidence of a nonlinear association for intake of processed meat, but not for intake of red meat.Findings from our meta-analysis indicate that consumption of red and processed meat may be related to NHL risk. More prospective epidemiological studies that control for important confounders and focus on the NHL risk related with different levels of meat consumption are required to clarify this association.

Risk of lymphoma subtypes and dietary habits in a Mediterranean area

BACKGROUND

Previous studies have suggested that diet might affect risk of lymphoma subtypes. We investigated risk of lymphoma and its major subtypes associated with diet in the Mediterranean island of Sardinia, Italy.

METHODS

In 1998-2004, 322 incident lymphoma cases and 446 randomly selected population controls participated in a case-control study on lymphoma etiology in central-southern Sardinia. Questionnaire interviews included frequency of intake of 112 food items. Risk associated with individual dietary items and groups thereof was explored by unconditional and polytomous logistic regression analysis, adjusting by age, gender and education.

RESULTS

We observed an upward trend in risk of lymphoma (all subtypes combined) and B-cell lymphoma with frequency of intake of well done grilled/roasted chicken (p for trend=0.01), and pizza (p for trend=0.047), Neither adherence to Mediterranean diet nor a frequent intake of its individual components conveyed protection. We detected heterogeneity in risk associated with several food items and groups thereof by lymphoma subtypes although we could not rule out chance as responsible for the observed direct or inverse associations.

CONCLUSIONS

Adherence to a Mediterranean diet does not seem to convey protection against the development of lymphoma. The association with specific food items might vary by lymphoma subtype.

Nutritional factors and non-Hodgkin lymphoma survival in an ethnically diverse population: the Multiethnic Cohort

Background/Objectives

To understand the possible effect of modifiable health behaviors on the prognosis of the increasing number of non-Hodgkin lymphoma (NHL) survivors, we examined the pre-diagnostic intake of major food groups with all-cause and NHL-specific survival in the Multiethnic Cohort (MEC).

Subjects/Methods

This analysis included 2,339 participants free of NHL at cohort entry and diagnosed with NHL as identified b cancer registries during follow-up. Deaths were ascertained through routine linkages to state and national death registries. Cox proportional hazards regression was applied to estimate hazard ratios (HR) and 95% confidence intervals (CI) for overall and NHL-specific mortality according to prediagnostic intake of vegetables, fruits, red meat, processed meat, fish, legumes, dietary fiber, dairy products, and soy foods assessed by food frequency questionnaire.

Results

The mean age at diagnosis was 71.8±8.5 years. During 4.5±4.1 years of follow-up, 1,348 deaths, including 903 NHL-specific deaths, occurred. In multivariable models, dairy intake was associated with higher all-cause mortality (highest vs. lowest tertile: HR=1.14, 95% CI 1.00–1.31, p_trend=0.03) and NHL-specific (HR=1.16, 95% CI 0.98–1.37) mortality. Legume intake above the lowest tertile was related to significant 13–16% lower all-cause and NHL-specific mortality, while red meat and fish intake in the intermediate tertiles was associated with lower NHL-specific mortality. No association with survival was detected for the other food groups.

Conclusion

These data suggest that pre-diagnostic dietary intake may not appreciably contribute to NHL survival although the higher mortality for dairy products and the better prognosis associated with legumes agree with known biologic effects of these foods.

Epidemiology and etiology of non-hodgkin lymphoma

Non-Hodgkin lymphoma (NHL) consists of many histologically and biologically distinct lymphoid malignancies with poorly understood, but possibly distinct, etiologies. The patterns of incidence and time trend vary not only by age, sex, and race/ethnicity in the USA, but also show significant geographic differences, suggesting the potential role of infectious agents, environmental factors, and lifestyle factors in addition to host genetic status in the development of NHL. Important pathogenetic mechanisms include immune modulation and chronic antigen stimulation. Epidemiologic studies in the past two decades have provided intriguing new insights on the possible causes of lymphoma and support the idea that there is some mechanistic commonality of lymphomagenesis, but significant etiologic heterogeneity clearly exists. This review presents a summary of the current understanding of the descriptive epidemiology and etiology of NHL and suggests areas of focus for future epidemiologic research.

A prospective analysis of body size during childhood, adolescence, and adulthood and risk of non-Hodgkin lymphoma

The etiology of non-Hodgkin lymphoma (NHL) is poorly understood. Obesity is associated with inflammation, a cytokine milieu conducive to lymphocyte proliferation, and has been associated with NHL risk in some epidemiologic studies. To prospectively examine NHL risk in relation to adult and earlier life obesity, we documented 635 incident NHL diagnoses among 46,390 men in the Health Professionals Follow-up Study and 1,254 diagnoses among 116,794 women in the Nurses' Health Study over 22 to 32 years of follow-up. Using multivariable Cox proportional hazards models, we estimated cohort-specific incidence rate ratios (RR) and 95% confidence intervals (CI) for risk of NHL and major histologic subtypes associated with cumulative average middle and young adult (ages, 18-21 years) body mass index (BMI) and adolescent and childhood somatotype. NHL risk was modestly increased in men (but not women) with a cumulative average middle adult BMI ≥ 30 kg/m(2) (vs. 15-22.9 kg/m(2); RR, 1.28; 95% CI, 0.92-1.77; Ptrend = 0.05). In meta-analyses across cohorts, higher young adult BMI was associated with increased risk of all NHL (pooled RR per 5 kg/m(2), 1.19; 95% CI, 1.05-1.37), diffuse large B-cell lymphoma (DLBCL), and follicular lymphoma (all Ptrend ≤ 0.02). Adolescent somatotype was also positively associated with all NHL, DLBCL, and follicular lymphoma in pooled analyses (all Ptrend ≤ 0.03), whereas childhood somatotype was positively associated with NHL overall among women only (Ptrend < 0.01). These findings in two large prospective cohorts provide novel evidence that larger body size in childhood, adolescence, and young adulthood predicts increased risk of NHL, and particularly of DLBCL and follicular lymphoma.