Obesity and multiple myeloma

Abstract

An exploratory study was conducted of common clinical conditions as predictors of subsequent cancer in 143,574 outpatients of a health maintenance organization (in California, USA). An association was noted between obesity, diagnosed in 14,388 patients, and the subsequent development of multiple myeloma (MM) in up to 21 years (33 cases observed, 21.3 expected based on the experience of the entire cohort; standardized morbidity ratio=1.55, 95 percent confidence interval [CI]=1.06–2.17). This association was evaluated further in a second cohort of 163,561 multiphasic-checkup examinees followed up for as many as 24 years. Body mass index (BMI) at entry examination was associated positively with the incidence of MM in White men (e.g., relative risk [RR]=1.07, CI=1.01–1.15 per unit increase in BMI; and RR=1.68, CI=0.75–3.78, comparing the highest with lowest quartile). This association was absent in White women, partially confirmed in Black men and women (BMI quartiles two, three, and four showed higher risk than quartile one), and not explained by the presence of diabetes mellitus. The association was reduced or absent with BMI based on reported greatest adult-weight, and in White women was inverse with BMI based on reported lowest adult-weight. Among subjects with more than one checkup, increased risk was associated directly with weight loss among White men and associated inversely with weight gain among Black women. These findings suggest that body build or nutritional status may be involved in the development of MM by mechanisms that are presently unknown. If increased weight is a causal factor, weight loss occurs later after the disease process begins.