Obesity and Risk of Hip Fracture in Adults: A Meta-Analysis of Prospective Cohort Studies

Background
Many observational studies assessed the association between obesity and risk of hip fracture in adults, but reported controversial results. Our goal was to evaluate the association between obesity and risk of hip fracture in adults by conducting a meta-analysis of prospective cohort studies.
Methods
Three databases, PubMed, Embase and Web of Science, were searched through May 2012 to identify eligible cohort studies. Either a fixed- or a random-effects model was used to calculate the pooled relative risk (RR) with its 95% confidence interval (95%CI).
Results
Fifteen prospective cohort studies involving a total 3,126,313 participants were finally included into this meta-analysis. Overall, adults with obesity compared with the normal weight group had a significantly decreased risk of hip fracture (RR: 0.66, 95% CI 0.57 to 0.77, P<0.001). Meta-analyses by the adjusted status of RRs also suggested adults with obesity compared with the reference group had a significantly decreased risk of hip fracture (adjusted RR: 0.48, 95% CI 0.39 to 0.58, P<0.001; unadjusted RR: 0.66, 95% CI 0.56 to 0.78, P<0.001). Subgroup analyses by gender suggested individuals with obesity had a significantly decreased risk for developing hip fracture compared with the reference group in both men (RR 0.54, 95% CI 0.48 to 0.60, P<0.001) and women (RR 0.70, 95% CI 0.58 to 0.84, P<0.001). No evidence of publication bias was observed in this meta-analysis.
Conclusions
This meta-analysis of prospective cohort studies suggests that obesity significantly decreases the risk of hip fracture in adults, and obesity is probably a protective factor of hip fracture in adults.

背景
既往多项观察性研究探讨了成人肥胖与髋部骨折风险之间的关联，但所得结果存在争议。本研究旨在通过对前瞻性队列研究（prospective cohort study）进行荟萃分析（meta-analysis），评估成人肥胖与髋部骨折风险的相关性。
方法
本研究检索了截至2012年5月的PubMed、Embase及Web of Science三大数据库，以筛选符合纳入标准的队列研究。采用固定效应模型或随机效应模型计算合并相对危险度（relative risk, RR）及其95%置信区间（95% confidence interval, 95%CI）。
结果
本荟萃分析最终纳入15项前瞻性队列研究，共计3126313名研究对象。总体分析显示，与体重正常组相比，肥胖成人的髋部骨折风险显著降低（RR=0.66，95%CI：0.57~0.77，P<0.001）。按相对危险度校正状态进行的亚组荟萃分析同样显示，与参照组相比，肥胖成人的髋部骨折风险显著降低（校正后RR=0.48，95%CI：0.39~0.58，P<0.001；未校正RR=0.66，95%CI：0.56~0.78，P<0.001）。按性别进行的亚组分析显示，无论男性（RR=0.54，95%CI：0.48~0.60，P<0.001）还是女性（RR=0.70，95%CI：0.58~0.84，P<0.001），肥胖个体的髋部骨折风险均较参照组显著降低。本荟萃分析未发现发表偏倚的证据。
结论
本项基于前瞻性队列研究的荟萃分析表明，肥胖可显著降低成人髋部骨折风险，肥胖或为成人髋部骨折的保护性因素。