Variation in Resting Metabolic Rate Affects Identification of Metabolic Change in Geographically Distinct Cohorts of Patients With ALS

Mapping the Evidence for Measuring Energy Expenditure and Indicating Hypermetabolism in Motor Neuron Disease: A Scoping Review

OBJECTIVE

To map the international methods used to measure energy expenditure of adults living with motor neuron disease (MND) and to highlight discrepancies when indicating hypermetabolism in the MND literature.

BACKGROUND

A decline in the nutritional status of patients is associated with exacerbated weight loss and shortened survival. Assessments of energy expenditure, using a variety of methods, are important to ensure an adequate energy intake to prevent malnutrition-associated weight loss. Assessments of energy expenditure are also commonly used to indicate hypermetabolism in MND, although these approaches may not be optimal.

METHODS

A protocol based on the Preferred Reporting Items for Systematic Reviews and Meta-analyses extension for Scoping Reviews Guidelines was developed. Three electronic databases (Medline [Ovid], CINAHL [EBSCO], and Web of Science) were exhaustively searched. Identified publications were systematically screened according to predefined PICOS eligibility criteria. The primary outcome was the identification of methods used to measure energy expenditure in MND. The secondary outcome was the identification of applications of energy expenditure assessments to indicate hypermetabolism in MND.

RESULTS

Thirty-two observational primary research publications were identified. Thirteen (40.6%) were longitudinal in design, with data on repeated measurements of energy expenditure presented in 3 (9.4%). Thirteen (40.6%) were case-control studies, of which 11 use a matched control group. Pulmonary function was used to assess eligibility in 10 publications. Energy expenditure was measured using indirect calorimetry (IC) in 31 studies. Discrepancies in the durations of fasted, measurement, and washout periods were observed. Of all included publications, 50% used assessments of resting energy expenditure to identify hypermetabolism. Bioelectrical impedance analysis was used to assess body composition alongside energy expenditure in 93.8% of publications.

CONCLUSIONS

Resting energy expenditure is most frequently measured using an open-circuit IC system. However, there is a lack of a standardized, validated protocol for the conduct and reporting of IC and metabolic status in patients with MND.

Persistent high levels of perceived fatigue are not associated with hypermetabolism in patients with amyotrophic lateral sclerosis

Objective: Fatigue is a common symptom in amyotrophic lateral sclerosis (ALS). Little is known about factors that contribute to fatigue, and whether levels of fatigue change throughout disease course. We aimed to determine associations between self-reported perceived fatigue and metabolic and clinical features of ALS, and perceived fatigue over the course of disease. Methods: This prospective study was conducted between July 2017 and March 2024. Baseline measures of self-reported perceived fatigue, metabolic rate, and clinical measures of disease were assessed in 117 participants with clinically definite or probable ALS. For comparison, fatigue and metabolic rate were collected from 107 control participants. Perceived fatigue was determined using the Fatigue Severity Scale (FSS). Metabolic rate was assessed using indirect calorimetry. Functional capacity and clinical progression were assessed using the ALS Functional Rating Scale-Revised (ALSFRS-R). Results: Baseline levels of perceived fatigue were greater in people living with ALS (plwALS) when compared to controls (5.44 vs. 2.55; p < 0.01). Perceived fatigue was higher in plwALS with lower ALSFRS-R scores and was not associated with measures of metabolism. For most plwALS, perceived fatigue remained high as functional capacity worsened. Conclusion: Our findings confirm higher prevalence of perceived fatigue in plwALS, with persistently high FSS scores reported by most patients during follow-up. High levels of fatigue were not associated with hypermetabolism, suggesting that metabolic rate is unlikely to be a primary contributor. Results highlight a need for further research to identify factors that contribute to fatigue in ALS, and options for improved fatigue management.