According to a study published in the American Journal of Epidemiology, the risk of developing non-Hodgkin’s lymphoma may be decreased by recreational physical activity and increased by obesity.
Non-Hodgkin’s lymphoma (NHL) is a form of cancer that begins in the cells of the lymph system, which includes the spleen, thymus, tonsils, bone marrow, lymph nodes, and circulating immune cells. Lymphocytes are the main cells in the lymph system and exist in two forms: B and T-cells. Each of these cells serves a specific function in aiding the body fight infection. B-cell NHL is the most common type of NHL; it involves cancer that originates in B-cells and affects their normal maturation.
In NHL an excessive amount of atypical (cancerous) lymphocytes accumulates in the lymph system. These lymphocytes can crowd and suppress the formation and function of other immune and blood cells. NHL is categorized by the type of lymphocyte it involves and further defined by the rate at which the cancer grows. The appearance of cells under a microscope indicates the growth rate. High-grade or aggressive NHL is the fastest growing, whereas low-grade or indolent lymphoma develops more slowly.
To determine whether physical activity or obesity influence the likelihood of developing NHL, researchers in Canada conducted a study among 1030 subjects with NHL and 3106 subjects without NHL. The NHL cases had been diagnosed between 1994 and 1997.
- Compared to subjects with the lowest level of recreational physical activity, subjects with the highest level of recreational physical activity were significantly less likely to develop NHL. The evidence was particularly strong for women. The most active women had a 41% reduced risk of NHL, and the most active men had a 21% reduced risk of NHL.
- Obesity (defined as a body mass index of 30 kg/m2 or greater) increased the risk of NHL in both men and women. Obese men were 59% more likely to develop NHL, and obese women were 36% more likely to develop NHL.
- There was also a suggestion that high caloric intake increased risk of NHL, particularly among men.
This study suggests that a lower risk of non-Hodgkin’s lymphoma may be added to the list of benefits provided by regular physical activity and maintenance of a healthy body weight.
Reference: Pan SY, Mao Y, Ugnat A-M et al. Physical Activity, Obesity, Energy Intake, and the Risk of Non-Hodgkin’s Lymphoma: A Population-based Case-Control Study. American Journal of Epidemiology. 2005;162:1162-1173.
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