Rheumatoid Arthritis Health Article

Definition

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease of unknown etiology that primarily targets synovial tissues. It is relatively common with a prevalence of approximately 1% in adults all over the world. RA shortens survival and significantly impacts on quality of life in most affected patients. As this definition implies, RA is a systemic disease with essentially all patients having some systemic features such as fatigue, low-grade fevers, anemia, and elevations of acute phase reactants (erythrocyte sedimentation rate [ESR] or C-reactive protein [CRP}). Despite these systemic features, the primary target of this disease is the synovium that is responsible for most of the protean clinical features. Synovial tissues proliferate in an uncontrolled fashion, resulting in excess fluid production and erosion of surrounding bone, as well as tendon and ligament damage.

Fortunately, the last decade has seen the landscape of treatment of RA change dramatically. Current therapies will result in substantial clinical benefit for most patients, particularly if they are diagnosed early and started on appropriate therapy.

Epidemiology

RA is seen all over the world with a remarkably consistent prevalence of 0.5 to 1% of adults. For reasons that are still unclear, the prevalence in women is two or three times greater than in men. RA can occur at any age, but onset before the age of 45 in men is uncommon. The relatively few, well-done inception cohorts that are available suggest that the yearly incidence of RA is approximately 40/100,000 for women and about half of that for men. These figures vary significantly based on the age of the cohort. The best available data suggest that the incidence of RA in women increases with age until approximately 45, then it plateaus. The incidence rate is much lower in young men, approximately one third that of women but increases steadily with age and approaches that of women in the over-65 age group. Since the incidence of RA increases or is stable with age and RA is a lifelong disease, the prevalence of RA increases with each decade. Recent data strongly suggest that the incidence of RA, particularly rheumatoid factor-negative RA, is decreasing. The reason or reasons for this are unclear, but if elucidated, could provide valuable insight into the etiology/pathogenesis of RA and would allow us to think, for the first time, about preventive strategies.

RA has a significant genetic component; therefore, it is not surprising that certain populations have been reported where RA is very unusual and others where it is very common. Most notably, cohorts have been described in rural Nigeria where no individuals are affected with RA; in contrast, a prevalence of RA of 5% in some studies of Chippewa, Yakima, and Inuit Native American tribes has been reported.