New light has been shed on the interplay between genes, environment and disease with the publication of an Israeli study on risk factors for non-Hodgkin lymphoma (NHL) in Jewish and Arab populations.

As of 2012, Israel ranked first in the world in NHL incidence rates. This blood cancer represents the fifth most common malignancy in Israel and the eighth most common malignancy among West Bank Palestinians.

Yet despite living in close proximity, the two populations tend to differ in terms of lifestyle, health behaviors and medical systems.

Israeli and Palestinian researchers, led by senior hematologist Dr. Ora Paltiel, director of the Hebrew University-Hadassah Braun School of Public Health and Community Medicine, conducted a large-scale epidemiological study of medical history, environmental and lifestyle factors among 823 Palestinian Arabs and Israeli Jews with B-cell non-Hodgkin lymphoma (B-NHL) and 808 healthy controls.

Until now, most epidemiological studies of NHL have been carried out in North American and European populations, with a few focusing on East Asian populations and very few on B-NHL in Middle Eastern populations.

Using data from questionnaires, pathology review, serology and genotyping, they uncovered some risk factors common to both populations and other factors unique to each population.

The data, reported in the peer-reviewed journal PLOS ONE, showed that in both populations, overall B-NHL was associated 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, 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.

The fact that risk factors operate differently in different ethnic groups raises the possibility that environmental exposures don’t have the identical effect in individuals of varying genetic backgrounds. But this could also be a function of many other factors such as diet, cultural habits, environmental and housing conditions.

“Apart from the scientific contribution that this research provides in terms of understanding risk factors for NHL, the study was an important research cooperation among many institutions,” said Paltiel.

Those institutions included Hadassah-Hebrew University Medical Center; Al Quds University; Augusta Victoria Hospital; Beit Jalla Hospital; Hebrew University; Palestinian Ministry of Health; Rambam Medical Center; Technion-Israel Institute of Technology; Chaim Sheba Medical Center; Meir Medical Center; and Tel Aviv University in Israel, and Mount Sinai School of Medicine in New York.

“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,” said Paltiel. “Epidemiologic research has the potential to improve and preserve human health, and it can also serve as a bridge to dialogue among nations.”

The study was supported by a MERC/USAID grant, by the Israel Science Foundation and by the Hadassah University Hospital Compensatory Fund.