Body Mass Index and Risk of Age-Related Cataract: A Meta-Analysis of Prospective Cohort Studies

Background
Age-related cataract (ARC) is the leading cause of blindness in the world. The relationship between body mass index (BMI) and risk of ARC is controversial across observational studies. We therefore performed this meta-analysis to evaluate the association between BMI and risk of ARC.
Methods
Eligible studies were identified through an electronic search of PubMed, Embase and the Cochrane Library. We pooled study-specific relative risks (RRs) and 95% confidence intervals (CIs) to determine the risk of ARC associated with BMI categories and per 1 kg/m2 increase in BMI.
Results
A total of 17 prospective cohort studies were included in the meta-analysis. The pooled RRs of ARC were 1.08 (95% CI, 1.01–1.16) for overweight and 1.19 (95% CI, 1.10–1.28) for obesity compared with normal weight. These findings were robust when stratified by sex, sample source, outcome types and confounders, while significantly differed by assessment of BMI and ARC, and duration of follow-up. The summary RR suggested that per 1 kg/m2 increase in BMI was associated with a 2% increased risk of ARC (RR 1.02, 95% CI 1.01–1.03). Pooled estimates of RRs consistently indicated a trend for subjects with a high BMI to develop posterior subcapsular cataracts (RR 1.19, 95% CI 1.06–1.35, for overweight; RR 1.50, 95% CI 1.24–1.81, for obesity; RR 1.04, 95% CI 1.01–1.06, per 1 kg/m2 increase in BMI) other than nuclear or cortical cataracts.
Conclusions
The overall findings suggest that elevated BMI may increase the risk of ARC, especially posterior subcapsular cataracts. Further trials are needed to investigate the effect of weight reduction in obese populations on the risk of ARC.

背景
年龄相关性白内障（Age-related cataract, ARC）是全球首位致盲性眼病。现有观察性研究关于体质量指数（body mass index, BMI）与年龄相关性白内障发病风险的关联结论尚存争议。因此本研究开展此项荟萃分析，以评估BMI与ARC发病风险之间的相关性。
方法
通过电子检索PubMed、Embase及Cochrane图书馆筛选符合纳入标准的研究。我们合并各研究的特异性相对危险度（relative risks, RRs）及95%置信区间（confidence intervals, CIs），以分析不同BMI分层及BMI每升高1 kg/m²对应的ARC发病风险。
结果
本荟萃分析共纳入17项前瞻性队列研究。与正常体质量人群相比，体质量超标人群的ARC合并相对危险度为1.08（95%CI：1.01~1.16），肥胖人群为1.19（95%CI：1.10~1.28）。按性别、样本来源、结局类型及混杂因素进行分层分析后，上述结果保持稳健；但在BMI与ARC的评估方式、随访时长分层下，结果存在显著异质性。合并相对危险度分析显示，BMI每升高1 kg/m²，ARC发病风险升高2%（RR=1.02，95%CI：1.01~1.03）。针对不同白内障亚型的分析显示，高BMI人群更易发生后囊下白内障（posterior subcapsular cataracts）：体质量超标者RR为1.19（95%CI：1.06~1.35），肥胖者RR为1.50（95%CI：1.24~1.81），BMI每升高1 kg/m²对应的RR为1.04（95%CI：1.01~1.06），而核性白内障（nuclear cataracts）及皮质性白内障（cortical cataracts）未观察到类似关联。
结论
整体研究结果提示，体质量指数升高可能增加年龄相关性白内障的发病风险，尤以针对后囊下白内障更为显著。未来仍需开展进一步临床试验，以探讨肥胖人群减重对ARC发病风险的影响。