Modifiable dementia risk score to study heterogeneity in treatment effect of a dementia prevention trial: a post hoc analysis in the preDIVA trial using the LIBRA index

Background: Selecting high-risk participants for dementia prevention trials based on a modifiable dementia risk score may be advantageous, as it increases the opportunity for intervention. We studied whether a multi-domain intervention can prevent all-cause dementia and cognitive decline in older people across three different levels of a modifiable dementia risk score. Methods: Prevention of Dementia by Intensive Vascular Care (preDIVA) is a randomised controlled trial studying the effect of multi-domain vascular care during 6-8 years on incident all-cause dementia in community-dwelling people aged 70-78 years. For this post hoc analysis, we stratified preDIVA participants in tertiles based on their baseline LIfestyle for BRAin Health (LIBRA) index, a modifiable dementia risk score. With Cox proportional hazards regression, the intervention effect on dementia was assessed. The effect on cognition was measured every 2 years with the Mini-Mental State Examination and Visual Association Test. Results: Dementia developed in 220 of 3274 (6.7%) participants. In participants with a low, intermediate and high LIBRA index, the hazard ratio (HR) of the intervention on incident dementia was respectively 0.71 (95% CI 0.45-1.12), 1.06 (95% CI 0.66-1.69) and 1.02 (95% CI 0.64-1.62). Also, when adding the non-modifiable risk factors age, education and sex to the index, results were comparable (respectively HR 0.88, 95% CI 0.54-1.43; HR 0.91, 95% CI 0. 57-1.47; HR 0.92, 95% CI 0.59-1.41). There was no statistically significant intervention effect on cognition during follow-up across the LIBRA groups. Conclusions: In the preDIVA study population aged 70-78 years, the LIBRA modifiable dementia risk score did not identify a (high-) risk group in whom the multi-domain intervention was effective in preventing dementia or cognitive decline.