Frailty can increase the risk of negative health-related outcomes in older adults. Protein supplementation may be an effective way to improve frailty, but there is disagreement about its effects on frailty.

To systematically evaluate the effects of protein supplementation on muscle mass, strength, and physical function in frail/pre-frail older adults.

Electronic databases of CNKI, Wanfang Data, CQVIP, PubMed, Embase, Web of Science, Cochrane Library, CINAHL and Medline were retrieved for randomized controlled trials (RCTs) of the effects of protein supplementation on muscle mass, strength and physical function in frail/pre-frail older adults published from inception to June 2022. After literature screening, the quality of eligible RCTs was evaluated, and from which relevant data were extracted. RevMan 5.4 was performed to explore the effects of protein supplementation on muscle mass, muscle strength and physical function in frail/pre-frail older adults. And for the outcome indicator of muscle strength (grip strength) , due to large amount of reported literature, this study will be based on the amount of protein supplementation (<30 g/d subgroup and≥30 g/d subgroup) , frailty status (pre-frailty subgroup, frailty subgroup, frailty and pre-frailty subgroup) , frailty assessment tool 〔frailty phenotype assessment tool (FP) subgroup and non-FP subgroup〕, population (Asian subgroup and European subgroup) , and mean age (70-<75 years subgroup, 75-<80 years subgroup, and 80-<85 years subgroup) for subgroup analysis to further explore the effect of protein supplementation on grip strength in different subgroups.

A total of 12 RCTs were included (2 literatures for pre-frailty, 3 literatures for frailty, 7 literatures for frailty and pre-frailty) , with a total of 833 older adults (422 in the protein supplementation group and 411 in the control group) . Meta-analysis results showed that protein supplementation improved gait speed in frail/pre-frail older adults〔MD=0.03, 95%CI (0, 0.06) , P=0.05〕, but in improving muscle mass (appendicular lean mass) , muscle strength (grip strength) , other physical functions (assessment results of balance test, the timed up and go test, Short Physical Performance Battery) and frailty scores, the differences were not statistically significant (P>0.05) . The results of subgroup analysis showed that the effect of protein supplementation on the grip strength of the Asian population subgroup was significantly different from that of the European population subgroup in between-group comparisons (χ²=5.76, P=0.02) .

Protein supplementation may improve gait speed in frail/pre-frail older adults, but it does not show a significant advantage in improving their muscle mass, muscle strength and other physical functions. It is recommended to further investigate the effects of longer durations of supplementation, different types of protein supplemented, different amounts of supplementation and different regional populations on older adults with different frailty states, in order to find the best pattern of protein supplementation and provide a more sufficient evidence-based basis for frailty management.

衰弱会增加老年人健康相关负面结果的风险，蛋白质补充可能是一个有效改善衰弱的途径，但目前关于蛋白质补充对衰弱的影响尚有分歧。

系统评价蛋白质补充对衰弱/衰弱前期老年人肌肉质量、肌肉力量和身体功能的影响。

全面系统检索中国知网、万方数据知识服务平台、维普网、PubMed、Web of Science、Embase、Cochrane Library、CINAHL、Medline各数据库建库至2022年6月发表的蛋白质补充对衰弱/衰弱前期老年人肌肉质量、肌肉力量和身体功能等方面影响的随机对照试验。筛选文献，对符合纳排标准的文献进行质量评价、数据提取，并采用RevMan 5.4进行Meta分析，以探讨蛋白质补充对衰弱/衰弱前期老年人肌肉质量、肌肉力量和身体功能等方面的影响。且对于肌肉力量（握力）这一结局指标，因报道文献较多，本研究还根据蛋白质补充量（<30 g/d亚组和≥30 g/d亚组）、衰弱状态（衰弱前期亚组、衰弱期亚组、衰弱及衰弱前期亚组）、衰弱评估工具〔衰弱表型评估工具（FP）亚组和非FP亚组〕、人群（亚洲人亚组和欧洲人亚组）、平均年龄（70~<75岁亚组、75~<80岁亚组和80~<85岁亚组）进行亚组分析，以进一步探讨不同亚组的蛋白质补充对握力的影响。

最终纳入12篇文献（2篇文献为衰弱前期，3篇文献为衰弱，7篇文献为衰弱及衰弱前期），共833例衰弱/衰弱前期老年人，其中蛋白补充组422例、对照组411例。Meta分析结果显示，蛋白质补充可以提高衰弱/衰弱前期老年人步行速度〔MD=0.03，95%CI（0，0.06），P=0.05〕，但在改善衰弱/衰弱前期老年人肌肉质量（四肢瘦体质量）、肌肉力量（握力）、其他身体功能（平衡能力、站立行走试验、简易体能状况量表评分）和衰弱评分方面，差异无统计学意义（P>0.05）；人群亚组分析显示，亚洲人亚组的蛋白质补充对握力的影响与欧洲人亚组相比，差异有统计学意义（χ²=5.76，P=0.02）。

蛋白质补充可以提高衰弱老年人的步行速度，但在改善其肌肉质量、力量和其他身体功能方面未显示明显优势。建议进一步开展更长补充时长、不同蛋白质类型、不同补充量、不同地区人群对不同衰弱状态老年人影响的研究，以期寻找最佳的蛋白质补充模式，为衰弱管理提供更充分的循证依据。