The study of the association of pain and fatigue is, on the face of it, a curiously confusing thing. In many illnesses, pain and fatigue might be concurrent; or a patient might experience a time lag between the experience of either: A change in pain could result in a simultaneous change in the amount of fatigue, or a change in pain may antedate a change in fatigue. Or perhaps a change in fatigue may precede a change in pain.
One would likely not find many objections to the hypothesis that pain results in fatigue due to the energy consumed by prolonged pain suppression and the need to reconcile pain. However, fatigue can just as easily be assumed as the cause of pain, as it renders patients less able to suppress and deal with the pain.
Then again, maybe we should call off this little debate: It could be that changes in fatigue and pain share random fluctuations, and follow no pattern—and certainly not each other.
A study published in this month’s issue of “Arthritis Care & Research” examined the course of pain and fatigue in one illness, rheumatoid arthritis (RA), over the course of a year. Pain and fatigue were measured on a monthly basis, and the authors concluded that pain and fatigue showed fluctuations that were synchronous; the relation between the two symptoms was not temporal. There was no time lag.
Others have studied the relationship between pain and fatigue utilizing daily—not monthly measurements:
• A 1997 article published in “Arthritis Care & Research” concluded that in RA patients there were no differences in pain and fatigue levels between days; and pain and fatigue variations could not be explained by a patient’s mood at any given time.
• However, a study published in 2010 in the “Journal of Pain” found that RA patients who experienced days with more positive events experienced lower levels of same-day fatigue and higher levels of next-day fatigue in women; but this was not observed for men.
• Articles published in the journal “Pain” in 2002 and the “Journal of Pain” in 2011 found that fibromyalgia patients experienced a daily variation in pain and fatigue that appeared mediated by stress and quality of sleep.
The jury may still be out as to whether sex differences play a role in fatigue and pain, as there is no agreement to be found in the current literature: A study published in the “Annals of Rheumatic Disease” in 2010 found that younger women with many roles to play on a daily basis in life were more vulnerable to the negative consequences of fatigue associated with RA. In contrast, in the latest study discussed above, there were no such sex differences appreciated.
Nonetheless, no matter whether pain is the egg and fatigue the chicken, both of these potentially debilitating symptoms, seen in a variety of diseases and chronic fatigue and pain syndromes, are often made worse or better by a variety of factors, including psychological factors. And health care professionals cannot assume that the treatment of one of these two will automatically cause the other to improve. Both pain and fatigue must be recognized and treated, as none of us can persist in the assumption that the amelioration of one will lead to the extinguishment