Medicine · 1 author, 2 centres
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This nationwide study of 5,811 South Korean adults aged ≥60 found that obesity (BMI ≥25 kg/m²) was significantly associated with radiologically-confirmed osteoarthritis (OA), with adjusted odds ratios of 1.73 for men and 2.76 for women compared to normal weight. The prevalence of OA was 7.9% in men and 29.6% in women, following a U-shaped curve across BMI categories. These findings support weight management as a strategy to reduce OA risk in older adults.
**Background:** Osteoarthritis (OA) is a chronic degenerative joint disorder affecting approximately 250 million people globally and is a leading cause of disability. While obesity is a well-established modifiable risk factor for OA, most epidemiological evidence comes from Western populations with high obesity prevalence. There is a lack of research on the association between obesity and radiologically-confirmed OA specifically in the South Korean older population, which tends to have a relatively low BMI. This study aimed to investigate this association using a nationally-representative sample.
**Methods:** Data were obtained from the 2010–2012 Korea National Health and Nutrition Examination Survey (KNHANES), a nationwide population-based survey conducted by the Korea Centers for Disease Control and Prevention. From 25,534 total participants, 6,455 were aged ≥60 years. After excluding 278 with missing BMI data and 366 with missing radiographic images, the final sample comprised 5,811 participants (2,530 men, 3,281 women). BMI was calculated from standardized anthropometric measurements and categorized per Asia-Pacific WHO guidelines: underweight (<18.5 kg/m²), normal weight (18.5–23 kg/m²), overweight (23–25 kg/m²), and obese (≥25 kg/m²). Radiographic OA was defined as Kellgren–Lawrence grade ≥2 on either knee or hip radiographs, graded independently by two specialized musculoskeletal radiologists. Multiple logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) after adjusting for age, comorbidities (hypertension, diabetes mellitus, coronary artery disease, stroke), lifestyle behaviors (smoking, exercise, alcohol), and socioeconomic status (residential area, household income, education level). Sampling weights were applied to account for the complex survey design.
**Key Results:** Overall, 7.9% of older men and 29.6% of older women had radiologically-confirmed OA. A U-shaped relationship was observed across BMI categories: OA prevalence in men was 9.0% (underweight), 6.8% (normal weight), 8.1% (overweight), and 9.1% (obese); in women, it was 24.5%, 21.6%, 27.1%, and 38.4%, respectively. After full adjustment (Model 4: age, comorbidities, lifestyle, socioeconomic status), compared with normal-weight individuals, the ORs (95% CIs) for OA in obese subjects were 1.73 (1.13–2.64) for men and 2.76 (2.13–3.56) for women. Overweight was also significantly associated with OA in women (OR 1.60, 95% CI 1.21–2.12) but not in men (OR 1.41, 95% CI 0.91–2.20). Underweight was not significantly associated with OA in either sex. The association remained consistent across all adjustment models, with obesity ORs ranging from 1.56 to 1.73 in men and 2.67 to 2.76 in women.
**Clinical Implications:** This study provides the first population-based evidence of a significant association between obesity and radiologically-confirmed knee and hip OA in the South Korean older population. The findings are consistent with prior studies in Western populations, though the observed ORs are somewhat lower than those reported in Western cohorts (e.g., ORs of 7.0–7.48 for obesity in some studies), possibly reflecting ethnic differences in body composition or OA pathophysiology. The high prevalence of OA in older women (29.6%) and the strong dose-response relationship with BMI underscore the importance of weight management as a preventive strategy. Given that South Korea is rapidly aging and OA is a major cause of disability and reduced quality of life, public health efforts to maintain appropriate body weight and reduce excessive weight should be prioritized. Limitations include the cross-sectional design (precluding causal inference) and restriction to the South Korean population (limiting generalizability to other ethnic groups).