THU0091 BODY MASS INDEX TRAJECTORY IN RHEUMATOID ARTHRITIS
Authors: G. Challener, E. Myasoedova, C. S. Crowson, R. Giblon, J. M. Davis III
Journal: Annals of the Rheumatic Diseases (2020)

Background: Obesity is a known risk factor for development of refractory rheumatoid arthritis (RA) [1]. While past studies have examined associations between BMI and disease activity [1, 2, 3], and rheumatoid cachexia is a well-recognized phenomenon, few studies have characterized BMI trajectory over the disease course of RA. Objectives: 1) To compare BMI trends between RA and matched non-RA subjects. 2) To determine predictors of BMI trends within RA subjects. Methods: The study population comprised Olmsted County, Minnesota residents with incident RA (age &gt; 18 years, 1987 ACR criteria met in 1995-2009) and non-RA subjects from the same underlying population with similar age, sex and calendar year of index. All subjects were followed until death, migration, or 01/July/2019. Follow-up was truncated for comparability. Generalized additive models with smoothing splines were used to illustrate trends in BMI measurements over time. Results: The study included 558 patients with RA (mean age 55.6 years, 69% female) and 556 patients without RA (mean age 55.7 years, 69% female). Mean BMI of patients with incident RA (28.8) was not significantly different from that of non-RA subjects (28.9). Models demonstrating time trends in BMI showed a significant decline in BMI over time in both cohorts (p&lt;0.001). A model including the interaction between RA/non-RA status and time revealed a significant interaction (p&lt;0.001), indicating that patients with RA have a larger decline in BMI per year than patients without RA. There was no significant difference in BMI trends over time between seropositive (RF/CCP) and seronegative RA patients (p=0.16). In examining sex differences in BMI trends, female RA patients demonstrated a steeper decline in BMI compared to men (p&lt;0.001). Figure 1. Time trends within BMI in the rheumatoid arthritis (RA) and non-RA cohorts, adjusted for age, sex, and calendar year of RA incidence Conclusion: Our findings demonstrate a significant decline in BMI over time in both RA and non-RA populations, with a significantly larger decline per year in RA patients. The decline in the RA population is most pronounced beyond 5 years from RA incidence. Given that the mean age of patients in this study at baseline was 56 years, the finding of declining BMI in the healthy population fits with prior studies that demonstrate that BMI tends to decrease in the elderly population [4, 5, 6, 7]. The greater extent of BMI loss in the RA population may reflect the phenomenon of rheumatoid cachexia. More studies are needed to understand the reasons and implications of these trends. References: [1]Liu Y, Hazlewood GS, Kaplan GG, et al. The impact of obesity on remission and disease activity in rheumatoid arthritis: a systematic review and meta-analysis. Arthritis Care Res (Hoboken). 2017; 69(2):157–65. [2]Sandberg MEC, Bengtsson C, Källberg H, et al. Overweight decreases the chance of achieving good response and low disease activity in early rheumatoid arthritis. Annals of the Rheumatic Diseases. 2014;73:2029-2033. [3]Sparks JA, Halperin F, Karlson JC, et al. Impact of bariatric surgery on patients with rheumatoid arthritis. Arthritis Care Res (Hoboken). 2015;67(12):1619–1626. [4]Vlassopoulos A, Combet E, Lean M. Changing distributions of body size and adiposity with age. Int J Obes. 2014;38:857-864. [5]Jiang T, Gilthorpe MS, Shiely F, et al. Age-period-cohort analysis for trends in body mass index in Ireland. BMC Public Health. 2013;13:889. [6]Wilson R, Abbott JH. Age, period, and cohort effects on body mass index in New Zealand, 1997-2038. Australian and New Zealand Journal of Public Health. 2018;42:396-402. [7]Song M, Zheng Y, Qi L, et al. Longitudinal analysis of genetic susceptibility and BMI throughout adult life. Diabetes. 2018;67:248-55. Disclosure of Interests: Gregory Challener: None declared, Elena Myasoedova: None declared, Cynthia S. Crowson Grant/research support from: Pfizer research grant, Rachel Giblon: None declared, John M Davis III Grant/research support from: Research grants from Pfizer, Consultant of: Served on advisory boards for Abbvie and Sanofi-Genzyme