Assessing the metabolic rate in patients with Amyotrophic Lateral Sclerosis, Progressive Muscular Atrophy, and Primary Lateral Sclerosis

OBJECTIVE: To determine whether resting energy expenditure (REE) differs between patients with amyotrophic lateral sclerosis (ALS), progressive muscular atrophy (PMA), and primary lateral sclerosis (PLS). METHODS: Patients with ALS, PMA, and PLS were enrolled between 2017 and 2021 in a prospective cross-sectional study. REE was measured by indirect calorimetry. Body composition was assessed using air displacement plethysmography and used to calculate predicted resting energy expenditure (pREE). Metabolic index (MI) was defined as mREE relative to pREE and expressed as a percentage. Differences between disease categories were assessed using multivariable regression adjusted for sex, age, fat-free mass, fat mass, height, and smoking status. RESULTS: = 0.019), with the highest mean observed in ALS (108.5%, 95% CI 105.8-111.1), followed by PMA (105.9%, 95% CI 102.6-109.3) and PLS (103.2%, CI 99.8 -106.6). Metabolic measures were not statistically correlated with disease-specific clinical characteristics. CONCLUSIONS: Our findings suggest that metabolic phenotype varies across MND subtypes. In the absence of non-neurological controls, findings are best interpreted as indicating that MI-defined hypermetabolism is most prevalent in ALS; however, whether metabolic rate is increased in PMA or PLS relative to the general population remains unknown.