Modifications to the frailty phenotype criteria: Systematic review of the current literature and investigation of 262 frailty phenotypes in the Survey of Health, Ageing, and Retirement in Europe

• The frailty phenotype has been frequently modified among studies.
• Physical inactivity and weight loss were the phenotypic criteria most often modified.
• Modifications have great impact on its classification and predictive ability.
• Among included phenotypes, frailty prevalence ranged from 12.7 to 28.2%.
• Areas under receiver operating characteristic curves for predicting mortality ranged from 0.607 to 0.668.

We conducted a systematic review to determine variability in how the criteria of the frailty phenotype (grip strength, weight loss, exhaustion, walking speed, physical activity) were assessed. We then evaluated the impact on estimating prevalence and mortality of modifying the criteria, using the Survey of Health, Ageing, & Retirement in Europe (SHARE). Five databases were searched for original research articles published after 2000, which evaluated frailty using the phenotypic criteria. Among the 264 included studies, 24 studies provided enough information to demonstrate that all criteria were assessed as proposed in the original frailty phenotype study by Fried et al. (2001). Physical inactivity and weight loss were the criteria most often modified. We then created 262 phenotypes from SHARE based on common modifications found in the review. Among these phenotypes, frailty prevalence ranged from 12.7% to 28.2%. Agreement with the primary frailty phenotype ranged from 0.662 to 0.967 and internal consistency ranged from 0.430 to 0.649. Women had 2.1–16.3% higher frailty prevalence than men. Areas under receiver operating characteristic curves for discriminating five-year mortality ranged from 0.607 (95% CI: 0.583–0.630) to 0.668 (0.645–0.691). The frailty phenotype often has been modified, and these modifications have important impact on its classification and predictive ability.