Aerobic fitness, fatigue, and physical disability in systemic lupus erythematosus.
OBJECTIVE
To measure aerobic fitness, muscle strength, fatigue, and physical disability in patients with systemic lupus erythematosus (SLE).


METHODS
Ninety-three patients with SLE and 41 sedentary controls were recruited into the study. Aerobic fitness was assessed by monitoring peak and submaximal oxygen uptake, heart rate, duration of exercise, and perceived exertion during a treadmill-walking test. Strength was measured using voluntary isometric quadriceps contraction. Symptomatic measures included physical and mental fatigue, mood, sleep, and functional incapacity.


RESULTS
Compared to sedentary controls patients with SLE had significantly reduced levels of aerobic fitness (mean VO2peak SLE patients, 23.2 ml/kg/min vs controls, 29.6 ml/kg/min; p < 0.001) and reduced exercise capacity (mean exercise duration SLE patients, 10.4 min vs controls, 13.1 min; p < 0.001). The SLE patients also had reduced muscle strength (mean maximum voluntary quadriceps contraction SLE patients, 298 N vs controls, 376 N; p = 0.003). Resting lung function was also significantly worse in the SLE patients (mean FEV, SLE patients, 2.6 l vs controls, 2.9 l; p = 0.002). Fatigue (p < 0.001), depressed mood (p < 0.001), poor sleep quality (p < 0.001), and functional incapacity (p < 0.001) were all significantly greater in the SLE patients. Linear regression models suggested that physical disability correlated with aerobic fitness (p < 0.001), fatigue (p = 0.005), body mass index (p = 0.01), and depression (p = 0.05) and that fatigue correlated with depression (p < 0.001).


CONCLUSIONS
Patients with SLE were less fit with reduced exercise capacity, reduced muscle strength, more fatigue, and greater disability compared to sedentary controls. Treatments developed to manage depression and improve aerobic fitness should be considered in the overall treatment of fatigue and disability in SLE.
Tench
Colin
C
Bone and Joint Research Unit, St. Bartholomew's, London, UK. Colin.Tench3@which.net
Bentley
David
D
Vleck
Veronica
V
McCurdie
Ian
I
White
Peter
P
D'Cruz
David
D
D000328:Adult; D004185:Disability Evaluation; D015444:Exercise; D005080:Exercise Test; D005081:Exercise Therapy; D005221:Fatigue / Q000209:etiology* / Q000628:therapy*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000150:complications* / Q000534:rehabilitation*; D010101:Oxygen Consumption; D010809:Physical Fitness; D011446:Prospective Studies; D012044:Regression Analysis; D012129:Respiratory Function Tests