Introduction
Muscular Dystrophy (MD) encompasses a group of inherited myogenic disorders characterised by progressive muscle wasting of variable severity and distribution affecting skeletal and cardiac muscle. Despite progress in gene therapies in pre-clinical models, curative treatments remain unavailable. However, advancements in clinical care have increased longevity in adults with MD, though loss of ambulation still occurs in 20-100% (1-3). We have recently observed that adults with MD consume less dietary protein than non-dystrophic individuals and, in MD, protein intake was positively associated with lean mass, grip strength and quality of life. In similar chronic conditions, mobility is a known barrier to nutritional adequacy(4), however the impact of mobility on habitual diet in MD remains unexamined. Therefore, the present study evaluated the impact of mobility on nutritional status in MD adults and probed for associations between nutrition, skeletal muscle parameters and quality of life (QoL) while considering mobility as a cofounding factor.
Methods
Secondary analysis from two adult MD cohorts (FSHD, LGMD, BMD, DM1), stratified by mobility: ambulatory (AB, n=37; 56±2 yrs; 27.4±4.5 kg/m²) and non-ambulatory (NAB, n=22; 54±2 yrs; 27.8±5.5 kg/m²) was conducted.Participants completed two three-day food diaries separated by eight weeks; a series of validated questionnaires assessing perceived functional ability and QoL; and a battery of physical assessments, including body composition, forearm muscle thickness, and various upper body strength measurements. Group differences were analysed using t-tests or Mann–Whitney U tests, correlations with Pearson’s r or Spearman’s ρ, and dietary intake distribution with linear mixed models with Bonferroni- corrected pairwise t-tests performed post hoc. Significance was set at p<0.05, corrected for multiple comparisons where appropriate.
Results
No differences were found between groups for BMI, lean mass percentage and self-reported physical activity (p>0.05). NAB reported lower absolute (g) (-16%, p=0.003) but not relative (g/kg) (-13%, p=0.088) protein intake, with no difference in total energy intake. NAB also reported lower protein intakes as a percentage of RDI (-24%, p=0.002) and derived less energy from protein (17% vs 19%, p= 0.005). Mobility had no significant effect on energy distribution across mealtimes; both groups consumed more energy at dinner than at lunch (+30%) or breakfast (+62%) (both p<0.001). A similar pattern was observed for relative protein intake, with dinner 0.07 g/kg higher than breakfast and 0.05 g/kg higher than lunch (both p<0.001). NAB exhibited 49–54% lower strength (all p<0.05) but similar forearm muscle thickness. Adjusted for mobility, relative protein intake (g/kg) correlated positively with lean mass (r=0.34, p=0.029), lower limb function (r= 0.386, p = 0.006), and QoL (r=0.353, p=0.013).
Conclusion
Non-ambulatory adults with MD exhibit lower absolute protein intakes than those who remain mobile, despite comparable energy intakes. This finding is particularly relevant, as dietary interventions such as increased protein consumption may exert a greater relative benefit in populations with reduced mobility by attenuating inactivity-induced declines in muscle mass and strength. As positive associations between protein intake, body composition, and QoL were observed irrespective of mobility status, nutritional interventions promoting adequate protein intake should be prioritised for all individuals with MD.