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Rheumatology 2001; 40: 70-73
© 2001 British Society for Rheumatology
Prevalence of large-joint osteoarthritis in Asian and Caucasian skeletal populations
Department of Orthopaedic Surgery, Shiga University of Medical Science, Otsu, Japan,
1 Service de Rhumatology, Hôpital Nord, Amiens, France,
2 Henan Provincial Institute of Cultural Relics and Archaeology Research, Zhengzhou, China,
3 Primate Research Institute, Kyoto University, Inuyama,
4 Rheumatology Clinic, Yukioka Hospital, Osaka, Japan and
5 Association pour les Fouilles Archaeologiques Internationales, Paris, France
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Abstract |
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Objective. To determine ethnic variations of large-joint osteoarthritis (OA) in past populations.
Methods. One thousand two hundred and nine adult skeletons, excavated from archaeological sites in Japan, China and France were assessed for OA as defined by the presence of eburnation.
Results. Within Asian skeletal populations, elbow OA and patellofemoral joint OA were more common in hunter–gatherers than in agriculturalists. Compared with Caucasians, the Asian skeletal population had a higher prevalence of tibiofemoral joint OA.
Conclusion. The relative frequencies of OA within and between ethnic groups at certain joint sites have changed over time from the past to the present.
KEY WORDS: Osteoarthritis, Paleopathology, Epidemiology, Asian Caucasian, Tibiofemoral joint, Patellofemoral joint, Elbow.
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Introduction |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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The prevalence of osteoarthritis (OA) appears to vary between ethnic groups. With respect to hip joints, OA is more common in Caucasians than in Japanese [1–3], whereas the prevalence of tibiofemoral joint (TF) OA is similar in the two groups [4–5]. Although we are aware of differences and similarities among various ethnic groups, the reasons are not well understood.
Our knowledge of OA may be increased by comparing paleopathological information about the disease with modern epidemiological data. However, because the definition of OA in skeletal samples has not been well established, a comparison between paleopathological studies of OA performed by different study groups will not provide reliable results. In the present study, we assessed OA findings in Japanese, Chinese and French skeletons excavated from archaeological sites, using consistent classification criteria. The prevalence of large-joint OA in Asian and Caucasian skeletal populations is reported.
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Materials and methods |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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The materials were human skeletal remains unearthed at several archaeological sites in Japan, China (along the Yellow River) and France. Their antiquity ranged from 5000 yr before present (BP) to 100 yr BP for the Japanese, from 7000 to 400 yr BP for the Chinese and from 1400 to 900 yr BP for the French samples. They were in store at the Laboratory of Physical Anthropology, Graduate School of Science, Kyoto University, Japan, Henan Provincial Institute of Cultural Relics and Archaeology Research, Zhengzhou, China and the archaeological site at Saleau, Picardy, France. The Asian skeletons were divided into two groups according to the underlying culture: gathering–hunting (Jomon Japanese and Ainu) and agricultural (Edo Japanese and all Chinese).
Age estimation and sex determination were made by an anthropologist (MN) for all Japanese and most Chinese specimens, by an archaeologist (ZQY) for some Chinese skeletons, and by an archaeologist (IC) for all French samples. For the Japanese and Chinese skeletons, the ages were categorized into three groups: 20–39, 40–54, and 55 yr or older. The French samples were divided into six groups: young (20–34 yr), young or middle-aged (Y/M), middle-aged (34–54 yr), middle-aged or old (M/O), old (55 yr or older), and adult (adult, but age undetermined). Sex-unknown skeletons, mixed-individual skeletons and those under 20 yr old were excluded. As a result, 1209 adult skeletons (402 Japanese, 394 Chinese and 413 French) were included in the study. The numbers of samples in each sex and age category are shown in Table 1
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The preservation status and presence of the following findings by visual examination were recorded for each joint site: eburnation, marginal osteophytes, pitting on the joint surface, and alteration in the bony contour of the joint. The joint sites observed were the glenoid, humeral head, distal humerus, proximal ulna, proximal radius, distal radius, acetabulum, femoral head, medial femoral condyle, lateral femoral condyle, medial tibial plateau, lateral tibial plateau, patellar surface of the distal femur, patella and distal tibia. Each Japanese skeleton was assessed by two observers (SH, KI) simultaneously, and the findings were recorded after agreement by both. Half of the Chinese skeletons were assessed by SH and the other half by KI. The French skeletons were assessed by KI.
OA was defined by the presence of eburnation. Since the samples had various degrees of damage and loss of bony elements, the prevalence of OA was calculated by joint (number of OA joints/number of observed joints).
Pearson's 
2 test and Fisher's exact test were used as appropriate. Statistical significance was inferred when the P value was less than 0.05.
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Results |
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The prevalence of OA by joint sites is shown in Table 2
. When Asian and Caucasian specimens were compared, OA was more often seen in Asians at the medial femoral condyle (0.8 vs 0.0%, P=0.05) and medial tibial plateau (1.0 vs 0.0%, P=0.03). At other joint sites, there were no significant differences between the two groups.
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Within Asian samples, OA was more common in hunter–gatherers than in agriculturalists at the distal humerus (2.7 vs 0.2%, P=0.002), proximal ulna (1.3 vs 0.0%, P=0.04), proximal radius (3.5 vs 0.3%, P=0.003) and patella (3.4 vs 0.5%, P=0.03). No significant difference was seen at the other joint sites (Table 2
). In view of contemporary epidemiological data, the prevalence of hip OA was compared separately between Japanese and French samples. Japanese skeletons tended to have a lower prevalence than the French at the acetabulum (0.3 vs 1.3%, P=0.11) and femoral head (0.2 vs 1.0%, P=0.13), although the difference was not statistically significant by Fisher's exact test.
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Discussion |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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A comparison between Asian and Caucasian samples showed a higher frequency of TF OA in the former. Within Asian populations, elbow OA and patellofemoral joint (PF) OA was more common in hunting–gathering than in agricultural populations.
Reliable measures for the definition of OA in paleopathology have not been established. We recorded the pathological findings in the manner described by Rogers and Waldron [6]. However, as they have pointed out [7], the inter-observer reproducibility of these findings is unsatisfactory, except for eburnation. In addition, most OA samples defined by the criteria of Rogers and Waldron show eburnation [6], which was also true in our series of samples. We therefore defined OA simply by the presence of eburnation.
A high frequency of elbow OA among hunting–gathering populations in North America has been noted in several reports [8–9]. In the present study, a higher frequency of PF OA was also found in Asian hunter–gatherers. Some factors responsible for elbow and PF OA could have been associated with the physical activity of these people. The results also suggest different aetiological factors between PF and TF OA.
In the French skeletal population, there were several skeletons with hip or PF OA, but none with TF OA. When only the Caucasian samples are considered, our findings are in accordance with the observations of Rogers et al. [10] and Waldron [11] that TF OA, which is very common in the present age, was uncommon in ancient British skeletons compared with hip and PF OA, and support their hypothesis that TF OA may be a disease of recent origin [10, 11].
Although the OA skeletons in the present study were not a large sample, the prevalence of TA OA was significantly higher in the Asian than in the Caucasian skeletal populations. Bias resulting from the age distribution of our samples would not influence these results, because, as Table 1 shows, there is no reason to consider that the proportion of older people might be higher in the Asian than in the Caucasian specimens. The factors responsible for this difference may be known or unknown risk factors for TF OA. Among the known factors in modern epidemiology, only knee-bending [12–15] could explain this discrepancy. Chair-sitting was already prevalent in Western populations during the period when the French skeletons in our study lived [16]. On the other hand, the use of chairs became prevalent in China during the Song Dynasty (about 1000 yr BP; personal communication from several Chinese archaeologists). In Japan, chairs were introduced during the Meiji period (about 130 yr BP), while Ainu hunter–gatherers did not use chairs. The present study included only five Asian (all Chinese) skeletons of people who lived in the period when chairs could have been used. Thus, the majority of the Asian samples must have been exposed to frequent knee-bending.
According to contemporary epidemiological data, the sex- and age-specific prevalences of TF OA in Japan, defined by the Kellgren–Lawrence scale, are similar to those in Caucasians [4, 5]. The interesting question is whether TF OA has increased during recent periods in Asia, as it probably has in Caucasian populations. If we suppose that it has increased in Asia, the most important risk factor for TF OA could be the contemporary lifestyle habits shared by Western and Eastern countries; if it has not, the major causative factor, other than knee-bending, might have travelled from East to West in the near-modern period. This question needs to be answered in further studies.
Despite the lack of statistical power in the present study, it is noteworthy that the prevalence of hip OA in the Japanese samples was very low compared with that in the Caucasian samples. The relative frequencies of hip OA in two ethnic groups in the past might have been similar to present frequencies [1–3]. Elucidation of changes in the relative frequencies of hip OA in different ethnic groups over historical periods should provide insight into the aetiology of hip OA.
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Acknowledgments |
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This study was supported in part by grants-in-aid for scientific research (09041180 and 10671356) from the Ministry of Education, Science, and Culture of Japan.
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Notes |
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Correspondence to: Dr K. Inoue, Department of Orthopaedic Surgery, Shiga University of Medical Science, Setatsukinowa-cho, Otsu, Shiga, 520-2192, Japan
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