Exploratory Analysis of the Relationships between Aerobic Capacity and Self-Reported Fatigue in Patients with Rheumatoid Arthritis, Polymyositis, and Chronic Fatigue Syndrome
Received 29 July 2008; accepted 22 April 2009.
Objective
To determine if self-reported levels of physical activity and fatigue are related to peak oxygen uptake (VO2peak) and whether these relationships differ among the patient groups (rheumatoid arthritis [RA], polymyositis [PM], and chronic fatigue syndrome [CFS]).
Design
Correlational investigation.
Setting
Two ambulatory research clinics at the National Institutes of Health, Clinical Center, Bethesda, MD.
Participants
There were 9 patients with PM, 10 with RA, and 10 with CFS. All patients met case criteria for their respective diagnoses.
Methods/Main Outcome Measurements
VO2peak during bicycle ergometry and self-reported fatigability, fatigue, and physical activity. VO2peak was used as the criterion measurement of physiological fatigue with which the self-reported variables were compared.
Results
The Pearson r revealed that self-reported physical activity correlated with VO2peak (r = 61, P = .01). However, fatigability and fatigue did not correlate with VO2peak. Linear regression analysis was performed to assess the effects of diagnosis group, self-reported activity level or fatigue, and their interaction. A trend in the data showed a distinctive relationship between fatigue/fatigability within the 3 groups. In addition, when controlling for group status, self-reported activity predicted aerobic capacity as measured by VO2peak.
Conclusions
This study confirms that patients with chronic, but stable RA, PM, or CFS are fatigued and have significantly decreased aerobic capacity. Self-reports of physical activity predicted VO2peak, and may be used as an indicator of activity-based aerobic capacity. Self-reports of fatigue, however, did not correlate with VO2peak and hence are assessing something other than an index of aerobic capacity, and provide additional information about patients' perceptions, which will require further investigation.
aCenter for the Study of Chronic Illness and Disability, 4400 University Drive, MSN 5B7, George Mason University, Fairfax, VA 22030†
bRehabilitation Medicine Department, Clinical Research Center, National Institutes of Health, Bethesda, MD‡
cDepartment of Statistics, George Mason University, Fairfax, VA§
dRehabilitation Medicine Department, Clinical Research Center, National Institutes of Health, Bethesda, MD¶
eClinical Research Program, Division of Allergy, Immunology and Transplantation, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health, Bethesda, MD∥
fLaboratory of Clinical Infectious Disease, NIAID, NIH, Bethesda, MD#
gCenter for the Study of Chronic Illness and Disability, George Mason University, Fairfax, VA⁎⁎
Address correspondence to: A.A.W.
Research supported by the Divisions for Intramural Research, Rehabilitation Medicine Department of the Clinical Center, and NIAID, National Institute of Health.
The present investigation did not use any medical devices.
This material was not presented at an AAPM&R Annual Assembly.
Disclosure Key can be found on the Table of Contents and at www.pmrjournal.org
ABSTRACT