A harmonized frailty index using global aging data

BACKGROUND: Frailty is a common syndrome among older adults, associated with multiple adverse health outcomes. Work harmonizing frailty measurement across 25 countries and regions and different socioeconomic environments is limited. A harmonized definition is needed to assess frailty across settings to inform comparative studies of health and healthcare. METHODS: Data on adults aged 50+ from 8 health and retirement surveys were analyzed: CHARLS (China), ELSA (England and Wales), ELSI (Brazil), HRS (USA), LASI (India), MHAS (Mexico), SHARE (Europe and Israel), and TILDA (Ireland). We produced a 30-item deficit accumulation frailty index (FI) from shared variables. We assessed within-survey distributions and, in 4 surveys with available data (HRS, MHAS, SHARE, and TILDA), association with mortality. RESULTS: A total of 184 715 participants were included; mean (SD) age was 65.1 (9.80) and 55.1% were female. Mean (SD) FI was 0.196 (0.133), and 39.2% were frail. Frailty distributions were right-skewed, with higher median FI for females than males (p < .0001). Kaplan-Meier analysis showed lower survival with greater frailty in studies with survival data. Hazard ratios (95% CI, p value) for severe frailty (FI ≥0.4) compared with non-frailty (FI <0.1) after adjustment for age, gender, and smoking status were 5.50 (4.89-6.19), 4.36 (3.67-5.18), 8.81 (6.44-12.05), and 3.97 (2.99-5.27) for HRS, MHAS, SHARE, and TILDA, respectively, all with p < .0001. CONCLUSIONS: This is a harmonized FI developed using data from multiple settings, with strong associations with mortality. This is a useful tool to better understand aging in a global context.