Sedentary Time, Physical Activity, and Sleep Duration: Associations with Body Composition in Fibromyalgia. The Al-Andalus Project

To explore the individual–independent relationships of sedentary time (ST) and physical activity (PA) (light and moderate-to-vigorous intensity (MVPA)), with sleep duration and body composition (waist circumference, body mass index (BMI), body fat percentage, and muscle mass index) in women with fibromyalgia, and to determine whether these associations are independent of physical fitness. This cross-sectional study involved 385 women with fibromyalgia. ST and PA were assessed by triaxial accelerometry, sleep duration was self-reported. Waist circumference was measured using an anthropometric tape, and body weight, body fat percentage, and muscle mass were estimated using a bio-impedance analyzer. In individual regression models, ST and sleep were directly associated with waist circumference, BMI, and body fat percentage (β between 0.10 and 0.25; all p < 0.05). Light PA and MVPA were inversely associated with waist circumference, BMI, and body fat percentage (β between −0.23 and −0.12; all p < 0.05). In multiple linear regression models, ST (β between 0.17 and 0.23), light PA (β between −0.16 and −0.21), and sleep duration (β between 0.11 and 0.14) were independently associated with waist circumference, BMI, and body fat percentage (all p < 0.05). MVPA was associated with waist circumference independent of light physical activity (LPA) and sleep duration (β = −0.11; p < 0.05). Except for MVPA, these associations were independent of physical fitness. These results suggest that longer ST and sleep duration, and lower PA levels (especially light intensity PA), are independently associated with greater adiposity, but not muscle mass, in women with fibromyalgia. These associations are, overall, independent of physical fitness.