Overweight and obesity have been associated with an increased risk of several malignancies. There is mounting evidence that a higher body mass index (BMI) increases the risk of developing non-Hodgkin lymphoma. However, the role of BMI on the incidence of diffuse large B-cell lymphoma (DLBCL) has not been extensively studied. The primary aim of our study is to evaluate the association between BMI and incidence of DLBCL using a meta-analysis of epidemiological studies. Secondary aims are to evaluate such association according to sex and geographical region.
A MEDLINE search through December 2010 was undertaken using (obesity OR “body mass index” OR BMI OR overweight) AND (lymphoma). Only epidemiological studies reporting on the incidence of DLBCL were included. Cross-sectional studies were excluded. Meta-analyses were performed for DLBCL in general, and according to sex and geographical region. The outcome was calculated as odds ratio (OR). Overweight was defined as BMI 25–29.9 kg/m2 and obesity as BMI 30 kg/m2, according to the WHO/CDC criteria. The random effects model (REM) was used to calculate the combined outcome. Heterogeneity was assessed by the I2 statistic. Publication bias was assessed by the trim-and-fill analysis. Meta-regression analyses were performed to evaluate the linear association between BMI as a continuous variable and DLBCL. Literature search and data gathering were performed independently by at least 2 of the investigators. All graphs and calculations were obtained using Comprehensive Meta-Analysis version 2 (Biostat, Englewood, NJ).
Our search rendered 13 studies; five case-control studies accounted for 4,399 cases and 22,298 controls, and eight prospective cohort studies accounted for 1,787 cases identified in a cohort of over 1.6 million individuals. Overweight individuals had an OR 1.14 (95% CI 1.04–1.25; p=0.01) of developing DLBCL. The OR of was significant DLBCL in overweight women (OR 1.23, 95% CI 1.07–1.42; p=0.004) but not in men (OR 1.12, 95% CI 0.78–1.60; p=0.55). Odds remained significant for American (OR 1.13, 95% CI 1.02–1.25; p=0.01) and Asian (OR 1.29, 95% CI 1.11– 1.51; p<0.01), but not for European individuals (OR 1.08, 95% CI 0.84–1.38; p=0.56). For obese individuals, the OR of DLBCL was 1.27 (95% CI 1.14–1.41; p<0.01). Obese women had an increased OR 1.24 (95% CI 1.06–1.46; p<0.01) but not men (OR 1.23, 95% CI 0.61–2.46; p=0.57). Odds remained significant in American (OR 1.32, 95% CI 1.18–1.48; p<0.01) and Asian (OR 1.35, 95% CI 1.08–1.68; p=0.01), but not in European population (OR 1.12, 95% CI 0.83– 1.51; p=0.46). Meta-regression analyses showed a relative OR of 1.014 per kg/m2 of BMI with a significant linear association with DLBCL incidence (p<0.01). No linear association was found in women (p=0.76) but there was a trend for men (p=0.07). A linear association was seen in American (p=0.01), there was a trend in Asian (p=0.06) but no association was identified in European individuals (p=0.46).
Based on this meta-analysis, an increased BMI is associated with a higher incidence of DLBCL. Such association appears stronger in women and in American and Asian populations.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.