Department of Orthopaedics, Orthopedic Research Institute, West China Hospital, Sichuan University, Chengdu 610041, China.
Nutrients. 2022 Apr 18;14(8):1674. doi: 10.3390/nu14081674.
Background: Iron overload is drawing attention in the development of knee osteoarthritis (OA). To identify the modifiable risk factors for iron-related pathological conditions, we examined the association between iron intake and the risk of knee OA progression. Methods: A total of 1912 participants in the Osteoarthritis Initiative (OAI), aged 45−79 years and with at least one knee radiographic OA at baseline, were identified and were followed up to 6 years. The iron and other nutrient intake was measured by the validated Block Brief 2000 Food Frequency Questionnaire. The outcome measures were by radiographic progression on the basis of the Kellgren−Lawrence (KL) grade and the joint-space-narrowing (JSN) score. The association between the iron intake and the knee OA progression was examined by Cox proportional hazards models and restricted cubic spline (RCS) regression. Results: Among the study participants, 409 participants experienced KL-grade progression, and 684 participants experienced JSN-score progression within 6 years. Overall, the association between iron intake and the risk of KL-grade progression followed a U shape (p for nonlinearity < 0.001). The risk of KL-grade progression was significantly lower in participants with iron intakes of <16.5 mg/day (per mg/day: adjusted hazard ratio (HR), 0.75; 95% CI (confidence interval), 0.64−0.89), and it was higher in those with iron intakes ≥16.5 mg/day (per mg/day: HR, 1.20; 95% CI, 1.04−1.38). Consistently, when the iron intake was assessed as deciles, compared to those in Deciles 3−5 (10.9−23.3 mg/day), the risk of KL-grade progression was higher for Deciles 1−2 (≤10.9 mg/day: HR, 1.57; 95% CI, 1.17−2.10) and for Deciles 6−10 (>23.3 mg/day: adjusted HR, 1.60; 95% CI, 1.19−2.16). Similar U-shaped relations were found for iron intake with the risk of JSN-score progression (p for nonlinearity = 0.035). Conclusions: There was a U-shaped association between the iron intake and the progression of knee OA, with an inflection point at about 16.5 mg/day, and minimal risk from 10.9 to 23.3 mg/day of iron intake. An appropriate iron intake was advisable for knee OA, whereas excessive or deficient iron intake increased the risk of knee OA progression.
铁过载在膝骨关节炎（OA）的发展中受到关注。为了确定与铁相关的病理情况的可改变风险因素，我们研究了铁摄入与膝 OA 进展风险之间的关系。
在 Osteoarthritis Initiative（OAI）中确定了 1912 名年龄在 45-79 岁且基线时有至少一个膝关节放射学 OA 的参与者，并对其进行了 6 年的随访。铁和其他营养素的摄入量通过经过验证的 Block Brief 2000 食物频率问卷进行测量。终点测量指标是基于 Kellgren-Lawrence（KL）分级和关节间隙狭窄（JSN）评分的放射学进展。通过 Cox 比例风险模型和限制性立方样条（RCS）回归检查铁摄入与膝 OA 进展之间的关系。
在研究参与者中，有 409 名参与者经历了 KL 分级进展，有 684 名参与者在 6 年内经历了 JSN 评分进展。总体而言，铁摄入与 KL 分级进展之间的关系呈 U 形（非线性 p<0.001）。每天摄入铁量<16.5 毫克（每毫克/天：调整后的危险比（HR），0.75；95%置信区间（CI），0.64-0.89）的参与者发生 KL 分级进展的风险显著降低，而每天摄入铁量≥16.5 毫克（每毫克/天：HR，1.20；95%CI，1.04-1.38）的参与者发生 KL 分级进展的风险更高。同样，当铁摄入量被评估为十分位数时，与 Deciles 3-5（10.9-23.3 毫克/天）相比，Deciles 1-2（≤10.9 毫克/天：HR，1.57；95%CI，1.17-2.10）和 Deciles 6-10（>23.3 毫克/天：调整后的 HR，1.60；95%CI，1.19-2.16）的 KL 分级进展风险更高。铁摄入与 JSN 评分进展之间也存在类似的 U 形关系（非线性 p=0.035）。
铁摄入量与膝骨关节炎的进展之间存在 U 形关系，拐点约为 16.5 毫克/天，每天摄入 10.9-23.3 毫克铁的风险最小。适当的铁摄入对膝骨关节炎是有益的，而过量或缺乏铁摄入会增加膝骨关节炎进展的风险。
