Epidemiology of Dementia

Dementia is one of the most important public health problems. Because of rapid increasing of old age in the world, need for prevention strategies and caring of dementia should be solved. Epidemiological studies can provide the basic data for making health policy, developing the prevention strategies. Epidemiological studies can be classified into the descriptive studies for studying the prevalence and incidence of a disease and the analytic studies for identifying risk factors of a disease. This review summarized the recent achievements in the epidemiology of dementia performed in the world and our country. The prevalence and incidence of dementia increased double by every 5 years of age over the age of 65 years in general. However, whether the prevalence rate of dementia exponentially increases in the oldest old age is uncertain. The prevalence rates of dementia were generally lower in developing countries, but the exact mechanisms of these findings were not well understood. Although Alzheimer’s disease is the most common etiology of dementia in most countries, some studies, especially from Japan, reported that vascular dementia is more common. However, recent studies suggested that the prevalence of vascular dementia decrease and Alzheimer’s disease is more prevalent. Age and some genetic factors were consistently reported as the risk factors of dementia. In contrast, the association between most non-genetic risk factors and dementia were still controversial. The epidemiological studies for dementia should overcome some methodological difficulties such as diagnostic threshold for dementia and the diagnostic criteria of vascular dementia.