Cognitive function measurement in online self-completion surveys: Evidence review

Cognitive function is a key determinant of health, economic, educational, and social outcomes across the life course. Incorporating measures of cognition into large-scale surveys enables researchers to track population trends, detect early signs of decline, and evaluate interventions. However, administering cognitive assessments in surveys is challenging. Many instruments are adapted from integrated sets of standardised psychometric assessments (or test batteries) used in a clinical context. These are typically designed for in-person administration. As surveys increasingly transition to web-based data collection, this creates significant difficulties, and there is strong evidence that cognitive assessments are particularly vulnerable to mode effects.