Obesity a minor player in rising rate of lymphoma

NEW YORK (Reuters Health) - The increasing number of cases of lymphoma and other cancers of the blood cannot be blamed to any great degree on the increasing number of people who are overweight or obese, Norwegian investigators conclude.

The rate of non-Hodgkin's lymphoma (NHL), which makes up a major proportion of all lymphomas, has risen during the last three decades in Norway and other parts of the world, Dr. Anders Engeland, from the Norwegian Institute of Public Health in Oslo, and colleagues explain in a report in the American Journal of Epidemiology.

Obesity has also increased worldwide during the past 30 years. This suggests obesity and lymphoma might be linked, but studies looking for ties between the two factors have yielded inconsistent findings.

To explore further, the team looked at height and weight for two million Norwegian men and women aged 20 to 74 years, who were measured at some point from 1963 to 2001. During an average follow-up of 23 years (maximum, 40 years), 24,500 cases of lymphoma were recorded.

Overall, the researchers found a "moderate and consistent" link between increasing BMI -- a measure of weight in relation to height -- and the risk of blood cancer in both men and women. Risk also increased modestly with increasing height.

With every five-unit increase in BMI, the risk of cancers of the blood rose 11 percent in men and 8 percent in women. For each 10-centimeter increase in height, the risk went up 19 percent in men and 16 percent in women.

Engeland and colleagues conclude, based on their findings, that the increasing incidence of overweight and obesity plays "only a minor role" in explaining the increased incidence of lymphomas seen around the world.

SOURCE: American Journal of Epidemiology, January 2007.