Estimating Premorbid IQ in Culturally and Linguistically Diverse Older Adults: A Critical Narrative Review

Estimating premorbid IQ is essential for determining whether current cognitive performance reflects decline from an individual’s likely level of functioning before neurological injury or disease, yet commonly used estimators may be less valid in culturally and linguistically diverse (CALD) older adults. This critical narrative review synthesizes direct, within-population validation, and contextual evidence across established premorbid-IQ methods, newer culturally grounded and informant-based approaches, and emerging computational, longitudinal, and harmonization directions. Direct evidence on diversity-related influences remains limited, whereas within-population validation is concentrated most strongly in language-specific word-reading measures; no single method has been sufficiently validated across heterogeneous CALD older adults. We therefore propose an evidence-informed structured multimethod framework organized around four clinical tasks: Select the quantitative estimator or estimators with the strongest individual applicability; Contextualize estimates using developmental, educational, linguistic, occupational, migration, and collateral information; Compare reasonably applicable estimates for convergence, divergence, and plausible sources of discrepancy; and Report the most defensible premorbid range, evidentiary weighting, and remaining uncertainty. Contextual information should inform applicability and relative weight rather than unsupported numerical corrections. The framework is intended to structure clinical reasoning while highlighting priorities for future validation research and has not itself been validated as a standardized clinical algorithm.