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Arthritis Care Res (Hoboken). 2016 Sep;68(9):1332-9. doi: 10.1002/acr.22827. Epub 2016 Jul 27.

Physical Fatigue, Fitness, and Muscle Function in Patients With Antineutrophil Cytoplasmic Antibody-Associated Vasculitis.

Author information

1
Centre for Translational Inflammation Research, University of Birmingham, Birmingham, UK.
2
School of Medicine and Dentistry, University of Aberdeen, Aberdeen, UK.
3
University of Amsterdam, Amsterdam, The Netherlands.
4
NIHR/Wellcome Trust Birmingham Clinical Research Facility, UHB NHS Foundation Trust, Birmingham, UK.
5
School of Healthcare Science, Manchester Metropolitan University, Manchester, UK.

Abstract

OBJECTIVE:

This study investigated differences in cardiorespiratory fitness, muscular function, perceived exertion, and anxiety/depression between patients and healthy controls (HCs) and assessed which of these variables may account for the fatigue experienced by patients.

METHODS:

Fatigue was measured in 48 antineutrophil cytoplasmic antibody-associated vasculitis patients and 41 healthy controls using the Multidimensional Fatigue Inventory (MFI-20), focusing on the physical component. Quality of life, anxiety/depression, and sleep quality were assessed by validated questionnaires. Muscle mass was measured by dual-energy x-ray absorptiometry scan, strength as the maximal voluntary contraction (MVC) force, and endurance as sustained isometric contraction at 50% MVC of the quadriceps. Voluntary activation was assessed by superimposed electrical stimulation. Cardiorespiratory fitness ( ˙Vo2 max and oxygen pulse [O2 pulse]) and perceived exertion (Borg scale) were measured during progressive submaximal exercise.

RESULTS:

Patients reported elevated physical fatigue scores compared to HCs (patients MFI-20 physical 13 [interquartile range (IQR) 8-16], HCs MFI-20 physical 5.5 [IQR 4-8]; P < 0.001). Muscle mass was the same in both groups, but MVC and time to failure in the endurance test were lower due to reduced voluntary activation in patients. Estimated ˙Vo2 max and O2 pulse were the same in both groups. For the same relative workload, patients reported higher ratings of perceived exertion, which correlated with reports of MFI-20 physical fatigue (R(2)  = 0.2). Depression (R(2)  = 0.6), anxiety (R(2)  = 0.3), and sleep disturbance (R(2)  = 0.3) were all correlated with MFI-20 physical fatigue.

CONCLUSION:

These observations suggest that fatigue in patients is of a central rather than peripheral origin, supported by associations of fatigue with heightened perception of exertion, depression, anxiety, and sleep disturbance but normal muscle and cardiorespiratory function.

PMID:
26713864
DOI:
10.1002/acr.22827
[Indexed for MEDLINE]
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