A guide to understanding dementia 7 Types of dementia Alzheimer’s is the leading cause of dementia in the UK; responsible for up to 70% of all dementia cases. A slowly progressive brain disease that actually begins well before the individual starts to show any symptoms. Vascular dementia is the second most common cause of dementia. Otherwise known as vascular cognitive impairment, those who are diagnosed with vascular dementia may not suffer memory loss in the early stages of the condition, but will instead have an inability to plan or make decisions, combined in many cases with poor or impaired judgement. Alzheimer’s disease Vascular dementia Other dementia 70% 17% 13% The most common forms of dementia