An in-depth study identifying risk factors for follicular lymphoma
The Lymphoma, Lifestyle, Environment and Family (LEAF) Study was conducted between 2011 and 2016 with the aim of better understanding the relationship between lifestyle, environmental, occupational, and genetic risk factors for follicular lymphoma.
People diagnosed with follicular lymphoma, a type of B-cell non-Hodgkin lymphoma, participated in the study, along with their unaffected siblings and spouses, to help identify associated risk factors. The study found that smoking, excess body fat, and oily fish consumption may increase risk of follicular lymphoma, while sun exposure appears to be protective.
Identified risk factors
Smoking was shown to have the clearest association with increased risk of follicular lymphoma, with both personal cigarette smoking and exposure to other people’s cigarette smoke as a child being factors. Smoking could increase risk of follicular lymphoma through changes in our genes. The same genetic abnormality often found in follicular lymphoma tumours has also been found to be more common in the white blood cells of people who smoke.
The LEAF study was the first to explore the relationship between patterns of body shape over a person’s life and risk of follicular lymphoma; while these patterns from age five to 70 years did not appear to influence risk, excess body fat in adulthood was found to have a modest association with increased risk of the disease.
While diets high in dairy foods, fats, or meat were not associated with risk of follicular lymphoma, people who ate higher amounts of oily fish were observed to be at increased risk. This may be due to the high levels of pesticides found in oily fish relative to other animal products. Other studies have found that a high level of the organochlorine pesticide dichlorodiphenyldichloroethylene (DDE) in blood is associated with increased risk of follicular lymphoma. The use of organochlorine pesticides in Australia was mostly phased out in the early 1990s. However, effects from these pesticides can remain in the environment and associated dietary sources for a long time. Although eating a higher amount of oily fish may increase the risk of follicular lymphoma, a healthy diet should still include fish.
While no relationship was found in the LEAF study between risk of follicular lymphoma and occupational exposure to pesticides, a prior Australian study and overseas studies have reported increased risk of follicular lymphoma among people with substantial pesticide exposure. Taken together, the evidence suggests that exposure to specific pesticides is associated with increased risk of follicular lymphoma.
The study also explored occupational exposure to extremely low-frequency magnetic field (ELF-MF) radiation emitted from industrial equipment, but no evidence of association with risk of follicular lymphoma was identified.
Consistent with prior studies, risk of follicular lymphoma was found to be reduced with higher sun exposure, especially sun exposure on weekends and holidays in the warmer months. This is potentially due to the anti-inflammatory activities of Vitamin D, a compound generated when we are outside in sunlight. Nevertheless, UV rays from the sun are a risk factor for skin cancer, including melanoma, and care should be taken to protect the skin and eyes from exposure to the sun.
Future directions
Cigarette smoking, excess body fat, and pesticide exposure are associated with increased risk of follicular lymphoma. Further action is therefore needed in global tobacco control, health promotion activities to maintain a healthy weight, and regulations on the safe use of pesticides. Moving forward, blood and saliva specimens have been analysed for genetic changes, and findings on their relationship with risk of follicular lymphoma will be shared when they are available.