Alzheimer's Disease

Alzheimer's disease is considered to be the commonest form of a group of illnesses that predominantly occur in later life and are referred to as “the dementias.” These illnesses have in common a progressive loss of brain function leading to the development of impairments in a number of cognitive and functional abilities such as memory, the use and understanding of spoken language, and the ability to undertake complex tasks. As dementia progresses, these impairments become increasingly severe with the eventual loss of everyday living skills, resulting in an inability to care for oneself. Changes in personality and behavior are also apparent. The exact course and characteristics of the dementia in an individual varies depending on the cause for the dementia and also because of individual differences. The majority of the dementias are rare before the age of 60, but the prevalence rates increase steadily in older age groups. The general consensus is that the occurrence of Alzheimer's disease should not be considered inevitable with increasing age, but rather it is an illness that is age related and affects a proportion of people. Summarized below is a compilation of prevalence data published in the Alzheimer's Disease International (1999) “Factsheet 3.” These figures are a conservative estimate with some studies suggesting that nearly 50 percent of people over the age of 85 have dementia.

Alzheimer's disease was named after Alois Alzheimer, who in 1906 described the clinical features and postmortem findings of the brain from an elderly person who had suffered from particular mental experiences prior to her death. On postmortem, she had a significant loss of brain tissue and many microscopic plaques and tangles in her brain. Later research established that the plaques, containing beta amyloid, and the neurofibrillary tangles, containing aggregations of a modified form of another protein called tau, are together the characteristic brain changes of what is now called Alzheimer's disease. It was later established that there was a relationship between the severity of the symptoms of dementia prior to death and the extent to which these plaques and tangles were present in the brain at postmortem. While among Caucasians Alzheimer's disease is considered to be the cause of over half of the cases of dementia, this may not be so across all cultures. Globally, Alzheimer's disease is of increasing concern because the number of people over age 65 years, and therefore at risk of dementia, is increasing. For developed countries, mean life expectancy is now in the late 70s. It has been estimated in the United States that 4.5 million people have Alzheimer's disease at present and, if trends continue, it is estimated that 13.2 million will have Alzheimer's disease by 2050 (see Herbert et al. 2003).