CMT/HMSN 1: Development of a model of fatigue in neuromuscular disorders: A long

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J Psychosom Res. 2007 May;62(5):571-9.

The development of a model of fatigue in neuromuscular disorders: A

longitudinal study.

Kalkman JS, Schillings ML, Zwarts MJ, van Engelen BG, Bleijenberg G.

Expert Centre Chronic Fatigue, Radboud University Nijmegen Medical

Centre, The Netherlands.

BACKGROUND: Severe fatigue is reported by the majority of patients

with three relatively common types of neuromuscular disorders.

OBJECTIVE: This study aimed to identify predictors of fatigue in a

longitudinal study and to develop a model of fatigue in patients

with three neuromuscular disorders.

METHODS: One hundred ninety-eight patients [60 facioscapulohumeral

muscular dystrophy (FSHD), 70 adult-onset myotonic dystrophy (MD),

and 68 hereditary motor and sensory neuropathy type I (HMSN-I)

patients] were studied twice during an 18-month period. Fatigue

severity was assessed by the Checklist Individual Strength. A

multidimensional assessment method was used, including self-report

questionnaires, a daily Self-Observation List, and physical activity

(actometer). Muscle strength was determined using the Medical

Research Council scale. Structural equation modeling was used to

develop and test a model of factors contributing to the persistence

of experienced fatigue.

RESULTS: Muscle strength, self-reported physical activity, sleep

disturbances, and pain at baseline contributed directly or

indirectly to fatigue and impairment at follow-up. Lower muscle

strength contributed to lower levels of physical activity, which, in

turn, contributed to fatigue severity. The model showed excellent

fit for the whole group of neuromuscular disorders. In FSHD, pain

also contributed to physical activity. A model with the actometer as

measurement for actual physical activity instead of self-report

showed an excellent model fit in FSHD and HMSN but an insufficient

fit in MD.

CONCLUSION: The model of perpetuating factors for fatigue in FSHD

and HMSN is different from the model in MD. The main difference is

in physical (in)activity. These differences have implications for

interventions based on these models.