Objectives: This study aimed to assess the association between obesity or changes in body mass index (BMI) and the risk of RA considering the abdominal obesity status.
Methods: We included individuals aged 23 to 60 who underwent a national health examination in 2012-2013 (baseline) and four years prior. Obesity was defined by a BMI ≥ 25 kg/m2. The change in BMI over 4 years was divided into quartiles. Cox proportional hazard analysis was performed to assess the association of obesity and BMI change with the risk of RA.
Results: A total of 6,207,246 subjects were included, and 7,859 incident cases of RA were identified. Obesity was associated with a reduced risk of RA in males (HR 0.78, 95% CI 0.71-0.85) and females (HR 0.91, 95% CI 0.85-0.97). In subgroup analysis according to abdominal obesity status, the associations were observed for obesity with normal waist circumference (WC) in males (HR 0.75, 95% CI 0.67-0.84) and females (HR 0.88, 95% CI 0.81-0.95). In terms of BMI change, compared to the stable BMI group (quartile 2), the third (HR 0.92, CI 0.85-0.99) and highest quartile (HR 0.89, CI 0.83-0.96) showed an inverse association with the risk of RA in females, particularly in those with normal WC.
Conclusion: Obesity was associated with a lower risk of RA, especially among individuals with a normal WC. Increased BMI was also associated with a lower risk of RA, but this association was mainly observed in females and specifically for those with normal WC.
Keywords: Abdominal obesity; Epidemiology; Obesity; Rheumatoid arthritis.
© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.