Obesity is associated with high rates of disability in the general population. The nature of the relationship between obesity and disability in systemic lupus erythematosus (SLE), a condition with a high background rate of disability, is unknown.
Data were from 2 interviews, 4 years apart, of a longitudinal cohort of individuals with SLE (n = 716 women). Body mass index (BMI) was calculated from self-reported height and weight; obesity was classified by usual (BMI ≥30) and revised (BMI ≥26.8) definitions. Three measures of functioning were examined: the Short Form 36 (SF-36) Health Survey physical function (PF) subscale, Valued Life Activities (VLA) Disability Questionnaire, and employment. Multivariate analyses controlled for demographics, SLE duration and disease activity, glucocorticoid use, depression, and comorbidities. Prospective analyses also controlled for baseline function.
At a BMI of ≥30, 27.8% of the subjects were obese; at a BMI of ≥26.8, 40.6% of the subjects were obese. Regardless of obesity definition, obese women exhibited poorer baseline function, with decrements ranging from 20-33% depending on the functional measure and obesity definition. With a BMI of ≥26.8, the adjusted SF-36 PF scores were 4.3 points lower for obese women (P < 0.0001), VLA difficulty was 0.09 higher (P = 0.01), and odds of employment were 80% of nonobese women (odds ratio 0.8, 95% confidence interval 0.5-1.1). At the 4-year followup, women who were obese at baseline had poorer function and experienced greater functional declines.
Obesity was associated with clinically significant negative effects on function, both concurrently and prospectively. This negative impact occurred at a lower BMI than is often considered problematic clinically. Because of the high rate of SLE-related disability, addressing preventable risk factors such as obesity may improve long-term SLE outcomes.