Zenodo · Jul 21, 2026
Development of the Rural Longevity Ecosystem Index (RLEI): A Composite Instrument for Evaluating Candidate Healthy-Aging Environments
By Furgiuele A
Regions popularly identified as exceptional healthy-aging environments — commonly termed “Blue Zones” — have never been evaluated using a standardized, scored instrument; designation has instead depended on a qualitative, retrospective, and largely non-replicable process. This paper introduces the Rural Longevity Ecosystem Index (RLEI), a nine-domain composite instrument designed to evaluate candidate healthy-aging environments on a comparable, reusable basis. The RLEI scores nutrition, physical activity, air quality, social cohesion, psychosocial stress, walkability, agricultural intensity, biodiversity and environmental quality, and healthcare access, combined using a three-tier weighting scheme organized by each domain's causal proximity to a single designated primary outcome: healthy aging, operationalized as functional independence (Katz Index of Activities of Daily Living) at age 80 and older, with longevity treated as a secondary outcome. Functional independence is deliberately excluded from the composite score itself and reserved solely as the outcome the index is validated against, avoiding the circularity of partly predicting an outcome with a component of that same outcome. We present the index's conceptual basis — including a directed acyclic graph of the underlying causal model — its domain structure and candidate indicators, and, as the paper's central contribution, a complete statistical validation plan covering internal consistency, construct validity, criterion validity, sensitivity analyses, and cross-site calibration. We are explicit that the current weighting scheme is an illustrative starting point, not an expert-elicited or empirically fitted set of values, and that the index's usefulness depends entirely on whether this validation plan, once executed, shows it predicts the outcome it claims to track. The RLEI is offered as reusable infrastructure for the field, not as a certification instrument for any single site.