Causes and Epidemology of Rhematoid Arthritis

About 1.3 million people in the United States are believed to have rheumatoid arthritis.

·            About 75% of these are women. Women are two to three times more likely to develop rheumatoid arthritis than men.

·            Rheumatoid arthritis affects all ages, races, and social and ethnic groups.

·            It is most likely to strike people 35-50 years of age, but it can occur in children, teenagers, and elderly people. (A similar disease affecting young people is known as juvenile rheumatoid arthritis.)

·            Worldwide, about 1% of people are believed to have rheumatoid arthritis, but the rate varies among different groups of people. For example, rheumatoid arthritis affects about 5%-6% of some Native American groups, while the rate is very low in some Caribbean peoples of African descent.

·            The rate is about 2%-3% in people who have a close relative with rheumatoid arthritis, such as a parent, brother or sister, or child.

Although there is no cure for rheumatoid arthritis, the disease can be controlled in most people. Early, aggressive therapy to stop or slow down inflammation in the joints can prevent or reduce symptoms, prevent or reduce joint destruction and deformity, and prevent or lessen disability and other complications.

Rheumatoid Arthritis Causes:

The cause of rheumatoid arthritis is not known. Many factors are involved in the abnormal activity of the immune system that characterizes rheumatoid arthritis. These factors include genetics (heredity), hormones (explaining why the disease is more common in women than men), and possibly infection by a bacterium or virus.

Common causes:

• The cause of rheumatoid arthritis (RA) is unknown

• People with a genetic predisposition to developing RA may experience an environmental event (such as infection) that triggers the development of the condition, after which an inappropriate self-directed immune response persists

• Infectious agents, immune regulatory and hormonal irregularities, and autoimmunity are among the factors currently being considered.

Epidemiology:

Incidence and prevalence

Incidence

• Women: 36/100,000

• Men: 14/100,000

Prevalence

• 5-15/100,000 in developed nations.

Demographics

Age

• Disease onset most common at 25-55 years of age

• Incidence rises with age

Gender

Women: men 2.5:1.

Race

There is a higher incidence (3-5%) in some native North American tribes (Pima, Yakima, Chippewa, and Inuit).

Genetics

• Patients with HLA-DRB1 alleles may have a poorer prognosis

• The condition clusters in families

• A shared epitope among several HLA-DR1 and HLA-DR4 alleles appears to predispose to the disease

• HLA-DQw7 has been proposed as an important marker gene

Geography

Remarkably constant worldwide, but slightly lower (0.3%) in China.

Socioeconomic status

Lack of formal education correlates with increased mortality in RA.