Abstract A79: Body shape throughout life, long-term weight cycling, and risk of multiple myeloma in the Nurses' Health Study

Abstract

Abstract Background: Multiple myeloma (MM) is a lethal malignancy with a poorly understood etiology. Adult body mass index (BMI) is a recently identified risk factor for MM, but the etiologic roles of body fatness at different ages and adult weight cycling have not been assessed. We prospectively examined body shape during childhood, adolescence, and adulthood, as well as weight cycling over a 20-year period, in relation to MM risk in the Nurses' Health Study (NHS) cohort. Methods: The NHS was formed in 1976 among 121,700 female registered nurses ages 30–55 years from the United States who returned the enrollment questionnaire on lifestyle and medical history. Biennial follow-up questionnaires have subsequently updated lifestyle and medical information. A validated somatogram-depicted body shape (current and at ages 5, 10, 20, 30, and 40 years) was queried in 1988. The 1992 questionnaire characterized weight change over the prior 20 years (when most NHS participants were middle-aged adults). The present analyses included women who completed the 1988 (somatogram) or 1992 (weight cycling) questionnaires and had no cancer history at that time. Women were followed through the earliest among a cancer diagnosis, death, or June 2008. We classified body shapes as relatively lean, medium, and heavier at the specified ages and for the average shape at ages 5 and 10 (“childhood”) and ages 10 and 20 years (“adolescent”). We classified women's 20-year weight cycling patterns as weight loser/maintainer, gainer (i.e., only weight gain), light cycler (i.e., net loss or gain of ≥5 lbs. with ≥1 episode of voluntary 5–9 lb. change), or heavy cycler (i.e., net loss or gain of ≥5 lbs. with ≥1 episode of voluntary ≥20 lb. change). We computed hazard ratios (HR) and 95% confidence intervals (CI) in Cox proportional hazard models to assess the association of body shape and weight cycling with MM risk. Models included only one body shape or weight cycling variable and controlled for potential confounding by age and baseline BMI. Results: We confirmed 126 incident diagnoses of MM over 1,049,600 person-years for the somatogram analyses and 96 incident diagnoses of MM over 749,578 person-years for the weight cycling analyses. We observed suggestive increases in MM risk among women who reported heavier average body shapes in childhood (v. those with a relatively lean childhood shape; HR=1.8; 95% CI=0. 8–4.2) and adolescence (HR=1.6; CI=0.6–4.1). Body shape at specific ages and at baseline did not appear to predict MM risk. In the 20-year weight cycling analysis, we observed a suggested modest increase in MM risk among women who were weight gainers (HR=1.2; 95% CI=0.5–3.0) or light (HR=1.2; 95% CI=0.5–2.8) or heavy cyclers (HR=1.4; 95% CI=0.6–3.2) compared to those who lost weight or maintained stable weight. Discussion: These first prospective studies of body shape at various ages and long-term adult weight cycling are consistent with existing evidence that obesity is positively associated with risk of MM. Obesity in adulthood has consistently predicted an increased risk of MM in published studies and is thus a potentially modifiable risk factor for MM. Obesity at younger ages or an inability to maintain stable adult weight may be predictors of adult obesity, or may indicate an etiologic role for earlier life exposures in MM. Confirmation of the present findings in men and in other large populations is warranted, as are studies to explore potential biologic correlates of these lifestyle factors. If confirmed, these data would suggest that maintenance of a healthy weight from an early age, in addition to conferring other health benefits, may help to diminish risk of MM. Citation Information: Cancer Prev Res 2011;4(10 Suppl):A79.