Fatigue is one of the most significant symptoms of rheumatoid arthritis (RA), perhaps second only to joint pain. It has been reported to affect 40 to 80 percent of RA patients. Possible causes for fatigue include anemia, inflammatory cytokines, pain, sleep disturbance, and depression. A recent medical journal article suggests that patients don't always complain about fatigue to their doctors, because they assume it's inevitable.
Since anemia has also been reported in about 50 percent of RA patients, a research team in Brazil looked for a correlation between anemia and fatigue. Anemia of inflammation is believed to be related to the body's sequestration of iron, as part of our defense against microbes. However, they found no association between hemoglobin levels and degree of fatigue. There was instead a correlation between fatigue and the Disease Activity Scores (DAS) for general health and number of swollen and painful joints.
Inflammation has been associated with fatigue in many situations. I know I always feel fatigued with any kind of infection: cold, flu, stomach bug, etc. A research group in Philadelphia studied fatigue in relation to inflammatory factors in RA patients, and found the following:
1. Weak association with erythrocyte sedimentation rate and swollen joint count
2. Weak to fair associations with tender joint count, physician global assessment of RA activity, and Disease Activity Score (DAS28)
3. Strong correlation with patient global assessment of severity
They concluded that fatigue is not an inflammatory variable.
A British group found that fatigue in RA patients is correlated with poor sleeping patterns, possibly due to joint pain and discomfort at night. These authors suggest more attention to treatment of insomnia.
Fatigue is also related to depression in RA patients. An article from University of Kansas School of Medicine recommends assessment of pain, fatigue, and depression together in rheumatology practice.
1. Escobar ME et al, “Anemia versus disease activity as cause of fatigue in rheumatoid arthritis”, Acta Rheumatol. Port. 2010; 35:24-8.