To examine relationships of obesity and physical inactivity to cognitive impairment in women with systemic lupus erythematosus (SLE).
Body composition was measured with dual x-ray absorptiometry (DXA) for 138 women with SLE. Obesity was defined by total percent body fat. Physical activity was ascertained with the self-reported International Physical Activity Questionnaire; inactivity was defined as expenditure of <600 metabolic equivalent minutes/week. Cognitive function was assessed with a 12-index neuropsychological battery. Impairment was defined as age-adjusted Z scores ≤1.5 SDs below the mean on 1 of 3 of tests completed. Scores were obtained for the total battery and for memory and executive function components. Multivariate analyses examined the relationship of obesity and physical activity, individually and combined, to cognitive impairment, controlling for education, race/ethnicity, disease activity, glucocorticoid use, and depression.
Fifteen percent of subjects were cognitively impaired, 28% were physically inactive, and 50% were obese. Five percent of active women were impaired on the executive function battery compared to 23% of those who were inactive (P = 0.003). Obese women were more likely to be impaired on the total battery (6% versus 23%; P = 0.007) and on the executive function portion (2% versus 19%) than nonobese women. In multivariate analysis, both inactivity and DXA-defined obesity were significantly associated with impairment in executive function (inactivity: odds ratio [OR] 9.4, 95% confidence interval [95% CI] 1.7-52.8; obesity: OR 14.8, 95% CI 1.4-151.0).
Both obesity and inactivity were significantly and independently associated with impairment in cognitive function. If longitudinal studies show that physical inactivity and obesity are precursors to cognitive impairment, these may become important targets for intervention.