Self-reported quality of life in progressive cognitive decline-let's not throw the baby out with the bathwater.

Assessing quality of life in progressive conditions like dementia presents unique challenges for Health Economics and Outcomes Research (HEOR). This commentary discusses current practices, highlighted by recent appraisals of lecanemab by NICE, where concerns about proxy-reported data-specifically, the risk of underestimating benefits-were noted as a limitation in the evaluation. While progressive cognitive decline complicates traditional self-reporting methodologies, emerging evidence demonstrates that adaptive strategies and technology-assisted methods can extend reliable self-reporting windows. The analysis identifies four critical challenges: (1) cognitive heterogeneity across dementia subtypes and stages clashing with HEOR's stable preference assumptions; (2) temporal fluctuations undermining single-timepoint assessments; (3) systematic discrepancies between self- and proxy-reported outcome data, inadequately addressed by current methods; and (4) the conceptual and psychometric limitations of current generic and condition-specific instruments. To address these challenges, the author advocates for a paradigm shift, inviting HEOR community to view diverse expressions of preference as a catalyst for innovation. This involves moving beyond static, binary preference assumptions to embrace dynamic, multimodal methods capturing non-verbal expressions in more advanced dementia. Proposed solutions include proxy calibration, an ecosystem of hybrid and graduated assessment integrating standardized domains with adaptable modules; reforming proxy protocols using Pickard's dual-gap framework to position proxy input as complementary, not substitutive; employing modern psychometrics and adopting relationship-centred engagement and process consent. Crucially, it calls for HEOR to integrate adaptive methods from adjacent fields-such as phenomenological inquiry, sensor technology, and data triangulation. These approaches can enhance the ability of HEOR to measure, value, and assess quality of life in the context of dementia and other progressive neurodegenerative conditions, ultimately anchoring value in lived experience and ensuring methodological limitations do not become barriers to accessing care and treatments.