Osteoarthritis (OA) is the most common form of arthritis in North America, and ranks among the top-ten causes of disability in the world. The majority of those afflicted include the elderly and women, resulting in pain, stiffness and activity limitations. It is a disease whose incidence is on the rise in this country as the population ages, and becomes more obese and less active. It should come as no surprise that this chronic pain condition is associated with substantial costs to the individual patient, and the entirety of the health care system; much of this is related to concomitant depression.
Of course, there have been many studies conducted in the attempt to elucidate risk factors responsible for a depressed mood in those suffering chronic pain. These have focused on variables such as gender, sleep quality, psychosocial factors, etc.. However, the independent relationship between pain and depressed mood has not been convincingly explored, particularly in arthritis patients.
While there have been a variety of studies published examining the relationships between pain, disability, and depression among individuals with painful OA, in addition to the impact exerted by social support, optimism, and personal control, there has been little data on the long-term influences of fatigue and disability. It is important that health care providers appreciate the outside-the-joint needs of the patient suffering joint pain, as this realization might go a long way to reducing the disease burden that so often accompanies what on the surface seems to be simply a "sore knee."
The authors of a recent article in this month's issue of "Arthritis Care & Research" sought to show that pain and depression are not just directly related, but that perhaps the major mechanism responsible for the undesirable outcomes in OA patients is because pain triggers a series of changes that result in depression. Thus, they examined patients with painful hip and knee OA, assessing the relationship between pain and depressed mood while controlling for psychosocial and other factors such as age, sex, etc., and considering OA-related fatigue and disability. Indeed, they found that pain leads to depression through effects on fatigue and disability; disability and apparently fatigue, but not depressed mood, lead to worsening of pain related to OA.
Further, the researchers concluded that chronic pain results in fatigue and disability, in turn causing depression. Fatigue is associated with poor sleep, and physical disability does not allow patients to participate in living; the outcome is depression. This should come as no surprise, for the inability to walk or care for oneself on a regular basis eliminates such simple joys such as visiting friends and family. Depression is associated with alterations in how pain is processed in the brain, causing patients to be more sensitive to pain stimuli. It may also be associated with less compliance with suggested pain therapies.
In other words, arthritis care needs input from our friends in the field of Psychology. Medical treatment of the symptoms and disability due to OA must be coupled with interventions which improve a given patient's ability to cope with pain, and which should block the effects of arthritis pain, and disability due to that pain, on depression.