Effects of Regional Variations and Occupation on Hand Osteoarthritis: Insights from the Research on Osteoarthritis/Osteoporosis Against Disability Study.

Objectives: This study aimed to investigate the prevalence of radiographic hand osteoarthritis (HOA) in older Japanese individuals in three distinct regions with unique geographic and occupational characteristics and explore the regional variations and factors, including occupational workload, that affect HOA.

Methods: We analysed the radiographic images and data of 1642 participants aged ≥60 years (mean, 75.6 years). After grading the radiographs of both hands using the modified Kellgren-Lawrence (KL) classification, HOA was defined as at least one joint with a KL grade ≥2, and severe HOA was defined as at least one joint with a KL grade ≥3.

Results: The overall prevalence rates of HOA and severe HOA were 95.9% and 54.2%, respectively. Regional differences were observed: residence in the mountainous region was associated with HOA and severe HOA, whereas residence in the coastal region was associated with only HOA. Occupational workload was associated with severe HOA in a dose-dependent manner, and heavy work was associated with a higher number of osteoarthritis-affected joints.

Conclusion: The present study revealed a high prevalence of HOA in older Japanese individuals and highlighted regional variations in HOA prevalence. A higher occupational workload was associated with a higher risk of severe HOA.