Dementia risk scores as surrogate outcomes for lifestyle-based multidomain prevention trials-rationale, preliminary evidence and challenges

Introduction: Although not designed as such, dementia risk scores might be useful surrogate outcomes for dementia prevention trials. Their suitability may be improved by using continuous scoring systems, taking into account all changes in risk factors, not only those crossing cut-off values. Methods: In three large multidomain dementia prevention trials with 1.5 to 2 years of follow-up (Multidomain Alzheimer Preventive Trial, Prevention of Dementia by Intensive Vascular Care and Healthy Ageing Through Internet Counselling in the Elderly) we assessed (1) responsiveness (sensitivity to change) and (2) actual and simulated intervention effects of the original and crude/weighted z-score versions of the cardiovascular risk factors, aging and incidence of dementia, and Lifestyle for Brain Health scores. Results: All versions of the risk scores were generally responsive, and able to detect small though statistically significant between-group differences after multidomain interventions. Simulated intervention effects were well detected in z-score versions as well as in the original scores. Discussion: Dementia risk scores and their z-score versions show potential as surrogate outcomes. How changes in risk scores affect dementia remains to be determined.