Increased height and weight might be risk factors for non-Hodgkin's lymphoma.
NHL is the sixth most commonly diagnosed cancer type in America.
The disease includes a number of different subtypes, all of which begin in the lymph.
The causes are not well understood, but some risk factors have been uncovered, including a suppressed immune system and exposure to certain types of infection.
Early symptoms include swollen lymph nodes in the armpit, neck and groin, in combination with fever, chest pain, night sweats and weight loss.
A recent study, conducted in Israel and published in the journal Cancer, adds to the current pool of knowledge regarding potential risk factors.
Over the past 30 years, a sharp rise in NHL cases has been noted. For instance, in Israel, incidence of NHL between 1990-2012 rose by 27%.
The reason for this increase is not yet understood, but it has prompted a flurry of research, especially within the countries that have been most affected.
Link between BMI and non-Hodgkin's lymphoma
Previous studies have uncovered evidence that a higher body mass index (BMI) might be related to an increased risk of NHL; however, many historical investigations relied on self-reported memories of past heights and weights.
The current research team, led by Dr. Merav Leiba of the Sheba Medical Center in Israel, set out to more accurately investigate the interaction of an individual's size in early adulthood and their future risk of developing NHL.
The investigators used data from the Israel National Cancer Registry, taken during compulsory medical board examinations. In total, 2,352,988 teens aged 16-19 were included; of these, 4,021 cases of NHL were reported.
The study found that being overweight or obese increased risk of NHL by 25%. Dr. Leiba said of the results:
"Obesity and overweight during adolescence are risk factors for future non-Hodgkin Lymphoma. It is important to be aware that overweight and obesity are not risk factors only for diabetes and cardiovascular disease but also for lymphomas."
The increase in risk for obese individuals is perhaps less surprising than the team's other finding: height also increased the risk of NHL. When compared with mid-range heights, shorter individuals showed a 25% reduced risk of NHL, while the tallest participants showed a 28% increase in risk.
How could height and weight impact lymphoma?
The exact mechanisms by which the height or weight of an individual raises their chances of NHL are not known and will require a great deal of additional research to unpick. Having said that, there are some reasonable theories that attempt to explain the phenomenon:
Weight and lymphoma
NHL is known to be heavily influenced by the state of the immune system. Both malnutrition and overnutrition can negatively impact an immune system's strength. Any wholesale effect on the immune system could be a contender.
Obesity carries with it a wealth of other physiological changes that could theoretically play a part in NHL's etiology, including insulin resistance, chronic inflammation and increases in insulin-like growth factor 1 (IGF-1).
IGF-1 is involved in growth during both childhood and adulthood; it also plays a role in modulating the immune system and preventing programmed cell death - the body's natural way of clearing out old and broken cells.
Dr. Leiba lists "oxidative stress, crosstalk between tumor cells and surrounding adipocytes, migrating adipose stromal cells, obesity-induced hypoxia and shared genetic susceptibility" as other potential players in the link between NHL and tumor formation.
Height and lymphoma
An increased risk of NHL in taller people initially seems a little harder to explain, but reasonable theories have been posited. Height is influenced by genetic factors, which, in turn, might play a role in disease etiology.
Height is also impacted by childhood nutrition and disease. Excess nutrition in early life has been linked to higher IGF-1 levels. Some theorize that a multitude of infections at a young age might divert resources into strengthening the immune system but funnel them away from increasing height. If this theory holds out, one might expect some taller people to be immunocompromised, and vice versa.
The evidence for an association between size and NHL has been strengthened by this study. The next challenge, and it is no small challenge, will be to tease apart the exact pathways that create this bridge.
Medical News Today recently covered research into new methods of disarming lymphoma's ability to avoid the immune response.