摘要Objective Frailty is becoming increasingly common among aging adults.Frailty transitionis shaped by biological,social,psychological,and environmental factors.This study investigated combined effects of protective factors on frailty transition by constructing a Protection Index(PI)to guide targeted interventions.Methods Data were extracted from the 4th Sample Survey of the Aged Population in Urban and Rural China,including baseline(2017)and follow-up(2019)surveys.Frailty was assessed using the Frailty Index(FI),whereas the PI measured protective factors.Frailty transitions over 2 years were analyzed prospectively.Pearson's correlation examined the relationship between FI and PI,andlogistic regression assessed the effects of PI on frailty transitions.Results This study included 9,093 older adults.FI values increased with age and were higher in women,whereas PI values decreased with age and were higher in men.Over 2 years,56.2％of the participants showed a stable frailty status,14.2％improved,and 29.6％worsened.Negative transitions were more common than positive transitions,with transitions occurring most frequently between adjacent states.The PI was moderately negatively correlated with the FI(r=-0.349,P＜0.001).A higher PI was associated with a lower risk of negative transitions among robust and prefrail individuals(OR=0.989,0.981,both P＜0.05),but showed no significant effect among those with existing frailty.Conclusion Negative frailty transitions were more common with advancing age.Enhancing PI may help prevent negative frailty transitions among robust and pre-frail older adults,underscoring the value of early interventions.