Association of food folate with asthma in US children and adolescents: a cross-sectional study

<b>Background：</b> Asthma is a chronic inflammatory disease. Currently, contradictory findings exist regarding the association between food folate and asthma. Therefore, we hypothesize a positive correlation between food folate and asthma. <b>Purpose</b>： To investigate the possible relationship between food folate intake and the development of asthma in children and adolescents in the United States. <b>Methods：</b> Data from the U.S. National Health and Nutrition Examination Survey (NHANES) from 2009-2018 were analyzed cross-sectionally by covariate adjustment using multivariate logistic regression, restricted triple spline curves, threshold effects, and stratified analyses. <b>Results:</b> There were 8,821 participants, of whom 1,697 (19.2%) self-reported having received a diagnosis of asthma from a physician or other health professional. After accounting for potential confounders, the adjusted odds ratios (ORs) for asthma in the second (T2, 111-178ug/day) and third (T3, &gt;178ug/day) groups were 1.15 (1-1.33) and 1.23 (1.04-1.46), respectively, compared with the group with the lowest food folate intake (T1, &lt;111ug/day). In addition, the association between food folate intake and asthma showed an inverse L-shaped curve (non-linear relationship, p = 0.003), and stratified analysis further validated the robustness of the results. The OR of asthma in subjects with food folate intake less than 263.9ug/day was 1.002 (1.001-1.004). <b>Conclusion:</b> In children and adolescents in the United States, there is a non-linear association (inverted “L” shape) between food folate intake and asthma, with an inflection point at 263.9 micrograms per day.

**背景**：哮喘是一种慢性炎症性疾病。目前，关于膳食叶酸（food folate）与哮喘之间的关联，已有研究结论存在矛盾。据此，我们提出膳食叶酸摄入与哮喘呈正相关的假说。**目的**：探究美国儿童及青少年群体中，膳食叶酸摄入与哮喘发病之间的潜在关联。**方法**：本研究对2009-2018年美国国家健康与营养检查调查（NHANES）的数据进行横断面分析，通过多因素logistic回归、限制性三次样条曲线、阈值效应分析及分层分析对协变量进行校正。**结果**：本研究共纳入8821名研究对象，其中1697人（19.2%）自述曾经医师或其他卫生专业人员诊断为哮喘。校正潜在混杂因素后，与膳食叶酸摄入最低组（T1，<111μg/天）相比，第二组（T2，111~178μg/天）与第三组（T3，>178μg/天）的哮喘校正比值比（OR）分别为1.15（1~1.33）和1.23（1.04~1.46）。此外，膳食叶酸摄入与哮喘的关联呈现倒L型曲线关系（非线性关联，p=0.003），分层分析进一步验证了研究结果的稳健性。当膳食叶酸摄入低于263.9μg/天时，研究对象的哮喘比值比为1.002（1.001~1.004）。**结论**：在美国儿童及青少年群体中，膳食叶酸摄入与哮喘存在非线性关联（倒"L"型），其拐点为263.9微克/天。