7. Project Summary/Abstract Discovering preclinical markers of cognitive and functional decline in mild cognitive impairment and dementia is fundamental for treatment development and to delay disease onset and progression. Subtle functional deficits on cognitively demanding activities often foreshadow dementia onset, but these early deficits are difficult to assess objectively with conventional methods. The proposed studies aspire to develop and validate performance-based indices for measuring functional deficits at older ages that are cost-effective, unobtrusive, and that could serve as early markers of subsequent cognitive decline and dementia. Specifically, we propose to develop indices of functional deficits that can be derived from participant response behaviors in existing population representative surveys. Completing a survey is a complex and cognitively demanding task that taxes a respondent's neuropsychological capacity. By focusing on how individuals complete surveys, we aim to derive a series of indices of functional deficits using two approaches: (1) The first approach consists of indices that are directly computed from participants' response patterns in questionnaires to capture invalid, incoherent, or erroneous responding on rating scales (examples include agreeing or disagreeing with statements regardless of content, skipping questions, or giving contradictory responses). (2) The second approach considers indices derived from individuals' computer use behavior in online surveys to measure the efficiency, speed, and consistency of behaviors during the completion of online surveys (examples include the proportion of corrected/changed answers, average response time, and response time variability). To evaluate the validity and clinical utility of the indices, we will systematically examine their associations with conceptually related constructs (concurrent cognitive test scores, instrumental activities of daily living, financial wellbeing, frailty), their sensitivity to change with age, their ability to predict subsequent cognitive decline, and their ability to predict the subsequent onset of mild cognitive impairment and dementia. Self-report surveys administered regularly in 16 existing longitudinal panel studies (>50,000 participants) will provide a rich basis for developing and testing indices derived from response patterns in questionnaires. An ongoing population representative Internet panel will provide the opportunity to test computer use behavior indices that are unobtrusively recorded “in the background” of online surveys. Marshalling multiple datasets and aggregating results across diverse samples and survey measures using identical data-analytic models will greatly enhance generalizability and test the breadth of applicability of each index. Examining the predictive accuracy of the indices alone and in concert will allow us to identify those indices that contribute substantial prognostic information and those that provide i...