The relationship of body habitus and respiratory function in Duchenne muscular dystrophy

The multidisciplinary care of Duchenne muscular dystrophy (DMD) incorporates management of nutrition and the respiratory system, however the effect of body habitus on respiratory function in DMD is poorly understood. The present study examined the impact of nutritional status on respiratory function in DMD to guide further treatment strategies.

Anthropometric and respiratory parameters, such as body mass index (BMI) z-scores, forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁) were retrospectively analysed with a mixed linear model in 34 DMD patients. Cross-sectional analysis of cough peak flow (CPF) in upright and supine positions and body fat mass were examined in 12 DMD patients.

Respiratory function in DMD patients was significantly related to BMI Z-score (P < 0.001), age (P < 0.05) and mobility (P < 0.001). DMD patients with greater BMI Z-score had increased respiratory function, even when adjusting for age and mobility status, with a 1 unit increase in BMI z-score associated with a 7.43% increase in FVC% predicted (P < 0.001). Body fat mass was adversely associated with FVC with a 1% body fat increase associated with a 1.5% reduction in FVC (P < 0.05). CPF values were significantly lower in supine compared to upright position (P = 0.005) and greater postural reductions in CPF were associated with higher body fat percent, with a 1% body fat increase associated with a 1.5% increase in postural CPF difference (P < 0.05).

The present study reinforces the importance of weight management in DMD, showing that a higher weight profile and lower adiposity have better respiratory outcomes. Furthermore, attention to body position with airway clearance techniques will maximize their effectiveness.