The association between body fatness and prevalent MGUS in the U.S. general population

Current evidence regarding the association between obesity and monoclonal gammopathy of undetermined significance (MGUS) remains inconsistent. This study aims to evaluate the relationship between objectively measured obesity markers and prevalent MGUS using nationally representative data from the U.S.

Data came from the third National Health and Nutrition Examination Survey III (1988-1994) and continuous NHANES (1999-2004). We estimated multivariable-adjusted odds ratios (aORs) and 95 % confidence intervals (CIs) for the association between MGUS and seven obesity markers (i.e., baseline body mass index (BMI), maximum lifetime BMI, waist circumference (WC), waist-hip ratio (WHR), total body fat, fat-free mass, and body fat percentage) using logistic regression. Body composition was assessed using dual-energy X-ray absorptiometry (DXA) in NHANES 1999-2004 and tetrapolar bioelectrical impedance analysis (BIA) in NHANES III.

The study included 200 participants with MGUS in NHANES III (1988-1994) and 164 with MGUS in NHANES 1999-2004, compared with 12,043 participants without MGUS. In multivariate logistic regression analysis with DXA measurements, each 1 %age point increase in body fat percentage was associated with a 4 % higher odds of MGUS (aOR: 1.04, 95 % CI [1.01, 1.07]) and a 6 % higher odds of non-IgM MGUS (aOR: 1.06, 95 % CI [1.02, 1.10]). No statistically significant associations were found between MGUS and other obesity markers, including baseline BMI, maximum lifetime BMI, WC, WHR, and fat-free mass.

Our findings indicate that obesity is associated with an increased odds of MGUS. However, many obesity markers, including the commonly used BMI, do not adequately capture this association.