Dementia: Introduction, epidemiology and economic impact

Dementia is a syndrome of progressive cognitive and functional impairment. It is caused by one or more neurodegenerative diseases, the most common of which are Alzheimer's disease (AD) and cerebrovascular disease (leading to vascular dementia). People with dementia suffer from diverse impairments and symptoms that affect them in different ways depending on dementia subtype and their personal and social circumstances. Memory is characteristically affected in Alzheimer's disease, but other dementias may present with behavioural or mood changes, communication or perceptual difficulties. Dementia onset may be sudden or it may be preceded by a stage of sub-dementia cognitive deficits, often termed mild cognitive impairment. Cost-of-illness studies aim to assess the economic burden of a disease and highlight the impact of the disease on society and provide important knowledge and guidance to decision-makers in prioritising their decisions regarding healthcare and prevention policies. There is increasing interest in examining the costs of dementia, and yearly reports are published regarding the worldwide cost. These reports synthesise the knowledge emerging from the studies assessing the cost of the disease in individual countries and show that, geographically, the majority of the studies are conducted in high-income countries, with 70 % being conducted in Western countries, mainly Europe and North America. More studies need to be conducted in low-income countries, because the prevalence of dementia in such countries is expected to significantly increase.