Scientists from Israel and the Palestinian Authority – whose leaders are most often vying with each other – have joined together to study risk factors in the two populations for B-cell type of non-Hodgkin lymphoma (NHL).Both populations report high incidences of NHL, which represents the fifthmost- common malignancy in Israel and the eighth-mostcommon malignancy among West Bank Palestinians.NHL tumors, which may originate from B or T lymphocytes, account for about 3% of all cancers in the world. But most epidemiological studies of it have been conducted in North American and European populations, with a few focusing on East Asian populations.Very few studies, however, have been conducted on B-cell non-Hodgkin lymphoma (B-NHL) in Middle Eastern populations.As Israelis and Palestinians represent genetically and culturally diverse populations living in the same region, research analyzing their risk factors can increase scientists’ understanding of genes and environment in causing lymphoma.Despite sharing the same ecosystem, the populations differ in terms of lifestyle, health behaviors and medical systems.As of 2012, Israel ranked first in the world in NHL incidence rates. The incidence rate is the number of new cases per population at risk in a given time period. When the denominator is the sum of the person- time of the at-risk population, it is also known as the incidence density rate, or person-time incidence rate. Now, Israeli and Palestinian researchers led by Prof. Ora Paltiel, dean of the Hebrew University-Hadassah Braun School of Public Health and Community Medicine and a senior doctor in Hadassah University Medical Center’s hematology department, have conducted an extensive epidemiological study examining risk factors for B-NHL and its subtypes in these two populations.Recruiting from both the Palestinian Arab and Israeli Jewish populations, the researchers looked at medical history, environmental and lifestyle factors among 823 people with B-NHL and 808 healthy controls. Using data from questionnaires, pathology review, serology and genotyping, they uncovered some risk factors common to both populations and others unique to each population.The data, just reported in the peer-reviewed journal PLOS ONE, showed that overall B-NHL was associated in both populations with: recreational sun exposure; black hair dye use; a history of hospitalization for infection; and having a first-degree relative with a blood cancer.An inverse association was noted with alcohol use.Some exposures, including smoking and greater- than-monthly indoor pesticide use, were associated with specific subtypes of B-NHL.The data also pointed to differences between the populations.Among Palestinian Arabs only, risk factors included gardening and a history of herpes, mononucleosis, rubella, or blood transfusion, while these factors were not identified in the Israeli Jewish population. In contrast, risk factors that applied to Israeli Jews only included growing fruits and vegetables and self-reported autoimmune diseases.The researchers concluded that differences in the observed risk factors by ethnicity could reflect differences in lifestyle, medical systems and reporting patterns, while variations by lymphoma subtypes infer specific causal factors for different types of the disease. These findings require further investigation as to their mechanisms, Paltiel said. The fact that risk factors operate differently in different ethnic groups raises the possibility of gene-environment interactions, that is, environmental exposures acting differently in individuals of different genetic backgrounds.But this divergence may reflect differences in diet, cultural habits, socioeconomic, environmental and housing conditions, medical services and exposure to infections in early life or other factors.This study reflects a unique joint scientific effort involving Israeli and Palestinian investigators, and demonstrates the importance of cooperative research, even in politically uncertain climates.Cancer epidemiology will be enriched through the broadening of analytic research to include under-studied populations from a variety of ethnicities and geographic regions.In addition to the Braun School and Hadassah University Medical Center and the Hebrew University of Jerusalem, the researchers came from Al Quds University; the Cancer Care Center at Augusta Victoria Hospital; Beit Jala Hospital; the Palestinian Health Ministry; the Tisch Cancer Institute and Institute for Translational Epidemiology of the Mount Sinai School of Medicine; Rambam Medical Center and Rappaport Faculty of Medicine at the Technion; Sheba Medical Center; Meir Medical Center; and Tel Aviv University.“Apart from the scientific contribution that this research provides in terms of understanding risk factors for NHL, the study entails an important research cooperation among many institution,” said Paltiel.“The study provided opportunities for training Palestinian and Israeli researchers and will provide for intellectual interaction for years to come. The data collected will also provide a research platform for the future study of lymphoma. Epidemiological research has the potential to improve and preserve human health, and it can also serve as a bridge to dialogue among nations,” he said.