ME-BYO index as a formative construct for healthy ageing: a cross-sectional PLS-SEM analysis.

Innovative health measures are essential for promoting "healthy aging." The "ME-BYO" index considers health to exist on a continuum scale rather than as a binary state. This investigation sought to validate the ME-BYO index as a formative construct, examining if its constituent domains appropriately reflect overall health status using empirical data from the Kanagawa Prospective "ME-BYO" Cohort Study. We analyzed cross-sectional baseline data from 4,218 participants (aged 18-95 years, mean age, 57.8; 55.5% female) in the ME-BYO cohort. The ME-BYO index was specified as a higher-order formative construct composed of body mass index; blood pressure construct (systolic blood pressure, hypertension history); the 5-item Geriatric Locomotive Function Scale (GLFS-5) for locomotor function; and the 6-item Kessler Psychological Distress Scale (K6) for mental health. Its association with subjective well-being, a composite outcome including quality of life and subjective happiness, was examined using structural equation modeling. The GLFS-5 (outer weight: 0.695, t = 35.47) and the K6 (0.617, t = 20.23) were the strongest indicators of the ME-BYO index. Higher scores on the ME-BYO index (showing worse health) had a strong negative relationship with the subjective well-being outcome (path coefficient: -0.676, t = 71.99), accounting for 45.7% of the variance (R²). The ME-BYO index is a structurally valid formative measure that combines indicators from locomotor, mental, and metabolic domains. Its significant capacity to reflect subjective well-being supports its practical application in health surveillance and as a tool for empowering individuals to manage their health proactively.