Risk Factors

Risk Factors

The prevalence in osteoarthritis increases as people age. In the U.S., about 60% of people over age 65 have some form of arthritis. Osteoarthritis and other arthritic conditions affect about 70 million American adults, about 21 million of whom are over 65 years old. With the growing population of older adults, experts expect that the number of arthritis sufferers will double by 2030.

Gender

Before age 45, osteoarthritis occurs more frequently in males (although it is not common in younger adults). After age 55, it develops more often in females. In a 2000 study, 33% of women had osteoarthritis compared to 25% of men. Some research suggests that women may also experience greater muscle and joint pain, in general, than men. And, women also tend to be undertreated for pain compared to men. The causes of such differences in pain sensitivity and treatment are largely unknown and most likely are due to a complicated mix of biologic, psychologic, and social factors.

Education

The incidence is highest in lower educational levels. In a 2000 study, 41% of adults with less than a high school education had arthritis compared to 21% of college graduates.

Geography

Although the average rate of osteoarthritis among older adults in the U.S. is 60%, it can vary widely in certain geographical regions. In the U.S., the rates in older adults are lowest (34%) in Hawaii and highest (70%) in Alabama. In general, the highest prevalence of arthritis in America occurs in the central and northwestern states.

Ethnicity and Inheritance

The rate of osteoarthritis varies by ethnic group. In the U.S., Caucasians and African Americans have higher rates of arthritis than Hispanics or other ethnic groups. Osteoarthritis also tends to favor specific joints over others in certain ethnic groups. The following are some examples:

• Older African American men are about 33% more likely than Caucasian men to have hip osteoarthritis. In one study, although men in both groups had equal risks for arthritic knees, African American men were more likely to have arthritis in both knees and to have more severe cases. Although comparable disparities in knee arthritis were observed between African American and Caucasian women, they might be explained by greater average weight among African American women. The study could not account for the differences among men, however.
• Asians appear to have a higher incidence of osteoarthritis in the knee, an equal risk for osteoarthritis in the spine, and a lower risk for osteoarthritis in the hips than Caucasians.