Thu Aug 8, 2002
NEW YORK (Reuters Health) - Elderly people in China appear to be 80% to 90% less likely to develop osteoarthritis of the hip than older people living in the US, a new study shows.
Experts hope the findings could shed some light on possible genetic or other biological factors that may be behind the development of the joint disease.
Osteoarthritis occurs when the cartilage that cushions joints breaks down, leading to pain and swelling. In the US, osteoarthritis is the leading cause of disability among the elderly, according to lead author Dr. Michael C. Nevitt of the University of California in San Francisco.
There is currently no cure for osteoarthritis, and treatment focuses on reducing symptoms.
In the current investigation, Nevitt's team surveyed 1,506 people age 60 or older who were living in Beijing. The men and women answered questions about joint pain and had pelvic X-rays. The results were compared to existing information on similarly aged US residents.
"We found that hip osteoarthritis was 80% to 90% less frequent than in white persons in the US," the authors write in the July issue of the journal Arthritis & Rheumatism.
The authors note that the rate of knee arthritis among people in the study was similar to those seen in US populations, so it doesn't appear that Chinese people have a lower rate of arthritis overall.
Possible reasons for the difference, the authors note, include differences in hip anatomy, as well as physical activity.
"Squatting is a traditional resting and working posture in China and is required for the use of non-Western toilets," they point out. It's possible, the researchers add, that the "extreme range of motion" required for squatting could stimulate cartilage regeneration.
But the authors note that Chinese people living in the US--who probably use the squatting position much less frequently than their counterparts living in China--also have a lower rate of osteoarthritis of the hip. Therefore, they add, it's possible that genetic factors also play a role. Another possible factor, they add, could be the fact that Chinese people are less likely to be obese.
"Like other studies comparing disease occurrence across geographic regions, our findings may provide clues to important pathogenic factors in osteoarthritis, factors which have likely not yet been fully appreciated," Nevitt and colleagues conclude.
SOURCE: Arthritis and Rheumatism 2002;46:1773-1779.