Several cohort studies have shown that vascular risk factors including hypertension, hypercholesterolaemia, diabetes mellitus, smoking, obesity and lack of physical exercise in midlife and to a lesser extent in late life, are associated with an increased risk of dementia. The results from randomised controlled clinical trials on treatment of these risk factors are not conclusive for the effect on cognitive decline and dementia. Studies investigating the effect of a multi-component intervention aimed at vascular risk factors to prevent or slow down cognitive decline and dementia will hopefully give the answer as to whether such an intervention is efficacious. This requires large clinical trials in an elderly population with long follow-up and several competing risks, making it difficult from an organisational and methodological point of view. Major challenges for future studies are to select the optimal population, set the optimal treatment targets and select clinically relevant outcome parameters.