Truncal fat distribution correlates with decreased vital capacity in Duchenne muscular dystrophy

Background: Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder associated with progressive muscle weakness and respiratory failure. Oral corticosteroids are the mainstay of treatment, but are associated with obesity with a central distribution. This study is designed to determine the relationship between body mass index, central adiposity, and lung function in subjects with DMD.

Methods: Retrospective fat distribution data was obtained in boys with DMD from studies using dual X-ray absorptiometry (DXA). Fat distribution data was reviewed at two tertiary academic institutions and compared with concurrent height, weight, body mass index (BMI), measures of lung function, and sleep study data when available. Truncal fat mass used as a measure of central adiposity.

Results: Forty-four subjects (age 12.0 ± 3.4 years) were included. Mean BMI was 22.1 ± 5.9 kg/m(2) . Sixty-eight percent (30 patients) were on corticosteroid therapy. Truncal fat mass percentage was inversely correlated with forced vital capacity (% predicted FVC) (Pearson coefficient -0.37, P = 0.01). Linear regression showed that truncal fat distribution, but not total fat mass, age or corticosteroid use negatively predicted FVC (r(2) = 0.24, P = 0.048). BMI had a positive effect (P = 0.04). However, fat distribution did not predict the rate of change of lung function in a smaller sample. Fat distribution, BMI, or age did not predict measures of sleep disordered breathing.

Conclusions: Truncal fat distribution is a significant predictor of lower vital capacity in boys with DMD, whereas BMI has a positive effect.