Body mass index (BMI) z-scores increase in patients with Duchenne muscular dystrophy (DMD) as they lose ambulation, according to study findings published in Neuromuscular Disorders.
DMD, which leads to muscle weakness (including the heart and lungs), is the most common inherited muscular dystrophy. In later disease stages, lean body mass decreases as fat mass increases, which often leads to obesity. Prior research does not show a clear relationship between ambulatory status, corticosteroids use, caloric intake, and BMI-z.
The objective of the current study was to analyze weight changes during DMD and the presence of any associations with ambulatory status, caloric intake, or corticosteroid use.
The researchers analyzed data of 159 male patients with DMD who annually visited 2 neuromuscular clinics in the Netherlands between January 2012 and March 2020.
At the first visit, 95 patients were ambulant and 54% of all patients used corticosteroids. Patients who were nonambulant were classified as overweight or obese (51%) compared with ambulant patients (44%). Six percent of ambulant patients and 9% of those nonambulant were underweight.
Caloric difference among the patients was 156±255 kcal/day. Higher caloric difference was associated with higher BMI-z scores among nonambulatory patients (r 0.36 P =.04), while height-z scores did not tend to change over time. Patients using corticosteroids tended to have higher BMI-z scores compared with those who did not (r 1.06 r 0.51 P =.02). The two groups did not have significantly different caloric intake.
The researchers found that BMI-z scores tended to increase between age 7 and age 12. BMI-z scores began increase around 1 year before loss of ambulation until 2 years after loss of ambulation.
In mixed model analyses, the researchers found that BMI-z scores increased 0.44 units in the year around loss of ambulation (P =.004). BMI-z scores were not associated with corticosteroid use or caloric intake.
Caloric intake tended to be less than national recommendations but above individual recommendations, particularly among patients younger than 16 years. Reported and recommended caloric intake decreased around age 10. Nonambulant patients tended to have lower caloric intake compared with ambulant patients.
Study limitations included use of BMI for estimating obesity, 2 different height measurements, inaccuracies in measurement and reporting of anthropometric measures, and 48-hour recall procedure misreporting.
“Obesity is a common problem in patients with DMD,” the researchers stated. “This study showed that even a year before losing ambulation, BMI-z scores increased.”
The researchers suggest earlier intervention strategies related to caloric intake to prevent obesity in this patient population. Furthermore, they recommend physical activities throughout all stages of disease activity as a preventative measure for overweight and obesity in the later stages.
Houwen-van Opstal SLS, Rodwell L, Bot D, et al. BMI-z scores of boys with Duchenne muscular dystrophy already begin to increase before losing ambulation: a longitudinal exploration of BMI, corticosteroids and caloric intake. Neuromuscular Disorders. Published online February 9, 2022. doi:10.1016/j.nmd.2022.01.011