Association between RBC folate and odds of osteoarthritis in adults aged 40-60 years

Although the association between red blood cell (RBC) folate and osteoarthritis (OA) is still controversial, relevant evidence is continuously emerging. This study aimed to examine the relationship between RBC folate levels and the incidence of OA in adults aged 40-60. This cross-sectional analysis involved 7708 adults from the National Health and Nutrition Examination Survey 2009-2018. The independent variable was RBC folate, which reflects long-term folate status, and the outcome variable was the odds of OA. A logistic regression model was used to evaluate the association between RBC folate levels and the incidence of OA. Additionally, subgroup analyses were conducted by race, gender, and body mass index. After adjusting for other potential confounding factors, there was a positive association between RBC folate and the incidence of OA (OR 1.0024, 95% CI 1.0012-1.0036, P < 0.0001). When RBC folate was divided into four equal groups, in the fully adjusted model, participants in the highest quartile had a significant higher odds of OA than those in the lowest quartile (OR 1.3157, 95% CI 1.0532-1.6436, P = 0.0191). In adults aged 40 to 60 years, there was a J-shaped relationship between RBC folate and the incidence of OA (turning point: 102 nmol/dL, OR 1.0403, 95% CI 1.0242-1.0566, p < 0.0001). This indicates that when the RBC folate level exceeds 102 nmol/dL, for every 10 nmol/dL increase, the odds of OA rises by 4.03%. Our findings showed a positive association between RBC folate and the incidence of OA in adults aged 40-60. Further studies are required to explore its underlying mechanism and confirm this correlation.