High blood pressure is the leading cause of death and disability worldwide and the leading modifiable risk factor for stroke and other cerebrovascular diseases. A very recent hypothesis in cardiology suggests that fluctuations in a person’s blood pressure over time are more strongly linked with stroke than the category of blood pressure (e.g. high, average, low). This variability in blood pressure may also impact dementia and vascular brain health, however, there have been very few studies so far on this topic. Our aim is therefore to test whether fluctuations in blood pressure are associated with dementia and vascular brain health, and secondly, whether the use of certain blood pressure drugs can promote better cerebrovascular health. To achieve our aims we will bring together researchers from 10 different studies in the US, France and The Netherlands. By thoroughly investigating existing data from these studies, we will help answer questions about blood pressure and brain health, and inform decisions on the best strategy to reduce dementia risk.