Hypermetabolism in motor neurone disease is associated with a greater functional decline but not weight loss

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Abstract

Objectives

Motor Neurone Disease (MND) is fatal neurological disease. Hypermetabolism (increased resting energy expenditure (REE)) and loss of body weight occur in MND. We aimed to determine whether hypermetabolism correlates with disease severity and weight loss.

Methods

Patients (n=44) and control participants (n=45) presented at the MND clinic at the CCR following an overnight fast. Body composition was assessed using air displacement plethysmography (BodPod; COSMED). REE was assessed by indirect calorimetry (Quark RMR, COSMED) and a metabolic index (MI;% change in measured REE versus predicted REE) determined. Hypermetabolism was defined as MI>120%. Disease severity was assessed using the Amyotrophic Lateral Sclerosis Functional Rating scale (ALSFRS-R) and respiratory function tests (RFTs). A subset of MND patients (n=30) returned for a repeat assessment ~4 months later.

Results

Hypermetabolism was more prevalent in MND (41%) when compared with control (18%) participants. In longitudinal analyses, hypermetabolism was not associated with a change in RFTs (including forced vital capacity, p=0.91 and sniff nasal pressure, p=0.40), loss of body weight (p=0.79) or a reduction in% fat mass (p=0.78). Strikingly, hypermetabolic individuals experienced a greater decline in ALSFRS-R over the sampling interval (p<0.01).

Conclusions

We confirm a greater prevalence of hypermetabolism in MND when compared with matched controls. Hypermetabolism in MND patients is associated with a greater functional decline but not a change in RFTs or weight loss. While challenging the notions that hypermetabolism is a consequence of respiratory dysfunction and that it contributes to weight loss, our emerging insights suggest that hypermetabolism contributes to disease progression. Thus, hypermetabolism could have major implications for quality of life and possibly disease survival. Ongoing studies aim to clarify the cause for and consequence of hypermetabolism in MND.

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