Our cross-sectional study involves a provincial representative sample of the middle-aged and older Tibet inhabitants, and the overall prevalence of RA was estimated as 6.30%. Although there was a difference in age between those who refused to take blood and those who took blood, the average age of the former is higher than the latter. At the same time, as we all know that the prevalence of RA increased with age, therefore the true prevalence may be higher. This amazing rate, which is close to the highest prevalence of RA (up to 6.80%) in the world which was identified in Native American Chippewa Indians , is far above a previously reported 0.28% (age-standardized prevalence) in the national epidemiological study in China . The prevalence in the over 45 years old group was much lower than our results also (0.74%). Similarly, both the prevalence of men (2.46%) and women (9.59%) in our research are higher than the study (0.19% in men and 1.28% in women, age > 45) . But the prevalence of women and totality increasing with age, and the peak being after 60 years old, which was consistent with previous reports. A study shown that the prevalence of RA has significant geographic variation . Considering that China is geographically a large area with a multi-ethnic population and substantial regional differences in socio-economic and hygienic conditions, the result may not represent China as a whole . Since 1983, a large number of studies have been performed in different areas of China to investigate the epidemiology characteristics of RA, with the focus on the differences among the different regions [15.16.17-26]. And the prevalence of RA ranges from 0.2%(Shantou) to 0.93%(Taiwan), which were all much lower than our results as well. However, the main concern of these researches was the prevalence in low altitude areas of the east-central China with different latitudes, and the majority of the participants were Han nationality .
Previous studies have presented that the prevalence of RA differs in different regions of the world, which suggested the aetiology of this disease was influenced by both gene and environment factors . Tibet is known as the ‘Third Pole’ and is one of the highest and most extreme inhabited areas of the world, which means the geographical environment of Tibet area is different from the inland or coastal areas of China . A research pointed out that the people living in high altitudes featured high bacterial diversity and richness, and Tibetans’ core microbiota comprised Prevotella . At the same time, Scher etc. identified that the presence of Prevotella as strongly correlated with disease in new-onset untreated rheumatoid arthritis (NORA) patients . Therefore, this might be a reason for the high prevalence of RA in Tibet. On the other hand, it is worth noting that nearly all of participants examined in our study were Tibetan residents (99.74%) of Luoma Town with the nomadic lifestyle. In addition, Tibet is an isolated area in the inland of China, where the plateau people live in for generations, which means that they have unique genetic background with low levels of heterozygotes, and high levels of homozygotes . As we all know, 50% of risk of developing rheumatoid arthritis is attributable to genetic factors . Maybe this could explain the much higher prevalence in Tibet compared to the other areas in China. And it is not just a coincidence: the prevalence of RA of native American Chippewa Band (6.8%) is far above that of the rest of the United States (1.07%), too [12, 34]. But more researches sre still needed to confirm it.
Our result demonstrates the prevalence of RA in Tibet with the highest rate. Therefore, Tibet as the key area of national medical poverty alleviation should be paid more attention to the prevention and treatment of RA. Meanwhile, the government should make policies based on the prevalence, disease burden  and local characteristics.