Association Between Body Mass Index and Myopia: Results from NHANES and Mendelian Randomization

<b><i>Purpose</i></b>: Previous studies have shown a conflicting association between body mass index and myopia. This study aimed to analyze the possible association between Body Mass Index (BMI) and myopia in the observational design and genetic evidence. <b><i>Methods</i></b>: In the observational investigation, 5,710 participants (12–25 years) from the 2001–2006 National Health and Nutrition Examination Survey (NHANES) were included. Weighted logistic regression models, restricted cubic spline (RCS) and stratified analysis were conducted in the NHANES. A two-sample Mendelian Randomization (MR) study using Genome-Wide Association Studies (GWAS) summary statistics and GWAS catalog was performed. The inverse-variance weighted (IVW) method was used as the main analysis method, and the sensitivity analysis was performed to detect pleiotropy and heterogeneity bias. <b><i>Results</i></b>: In the fully adjusted model, individuals with obesity had a higher risk of myopia [<i>OR</i> = 1.253, 95% <i>CI</i>= (1.049, 1.496), <i>p</i> = 0.014] and mild and moderate myopia [<i>OR</i> = 1.305, 95% <i>CI</i>= (1.094, 1.558), <i>p</i> = 0.004]. BMI was correlated with refractive spherical equivalent and showed a linear relationship (<i>P</i> for nonlinearity = 0.468, <i>p</i> = 0.002,β=-0.016). In males, obesity had an association with myopia, while there was no statistical significance in females. In the subgroup with an education level of &lt; 9th Grade, obesity and myopia exhibited consistent results. Two-sample MR showed that obesity had no statistically significant with myopia and refractive error. <b><i>Conclusions</i></b>: This study suggests that the associations between BMI and the risk of myopia differ based on gender and education levels in an observational study, while there are no associations in genetic evidence.

<i><b>研究目的</b></i>：既往研究关于体质量指数与近视的关联结论存在分歧。本研究旨在通过观察性研究设计与遗传学证据，分析体质量指数（Body Mass Index, BMI）与近视之间的潜在关联。
<i><b>研究方法</b></i>：观察性研究纳入了2001-2006年美国全国健康与营养调查（National Health and Nutrition Examination Survey, NHANES）的5710名年龄12-25岁的参与者。本研究在NHANES数据中采用加权logistic回归模型、限制性立方样条（restricted cubic spline, RCS）分析及分层分析；同时利用全基因组关联研究（Genome-Wide Association Studies, GWAS）汇总统计数据与GWAS目录开展两样本孟德尔随机化（Mendelian Randomization, MR）研究，以逆方差加权（inverse-variance weighted, IVW）法作为主要分析手段，并通过敏感性分析检测多效性与异质性偏倚。
<i><b>研究结果</b></i>：在完全校正模型中，肥胖个体罹患近视的风险更高[比值比（odds ratio, OR）=1.253, 95%置信区间（confidence interval, CI）=(1.049, 1.496), p值=0.014]，轻度及中度近视的发病风险亦显著升高[OR=1.305, 95%CI=(1.094, 1.558), p值=0.004]。体质量指数与屈光球镜当量呈显著相关，且呈现线性关系（非线性检验的P值=0.468, p值=0.002, β=-0.016）。亚组分析显示，男性群体中肥胖与近视存在统计学关联，而女性群体未观察到显著差异。在受教育程度低于9年级的亚组中，肥胖与近视的关联结果保持一致。两样本孟德尔随机化分析结果表明，肥胖与近视及屈光异常均无统计学显著性关联。
<i><b>研究结论</b></i>：本研究提示，在观察性研究中，体质量指数与近视风险的关联因性别与受教育程度而异，但遗传学证据未显示二者存在显著关联。