Alzheimer's Disease - Prevalence
Alzheimer's Disease (AD) is the most common form of dementia. Dementia is a brain disorder that seriously affects a person's memory, thinking, and reasoning skills. People with dementia often have trouble thinking and speaking clearly, remembering recent events, and learning new things. Over time, it becomes hard for them to handle everyday activities. There are many causes of dementia, but Alzheimer's disease is the most common cause of dementia in older persons. Amyloid plaques and neurofibrillary tangles in the brain are considered signs of Alzheimer's disease. Other brain changes in people with Alzheimer's disease include a loss of nerve cells and pathways in areas of the brain that are vital to memory and other mental abilities. Alzheimer's disease may disrupt normal thinking and memory by blocking messages between nerve cells.
Alzheimer's disease is not simply caused by the dyfunctional genes received from a person's parents. Even if several members of a family have in the past been diagnosed as having Alzheimer's disease, this does not mean that another member of the family will necessarily develop it, as the majority of cases of Alzheimer's disease are not genetic. However, as the disease is so common in the elderly, it is not unusual for two or more family members over the age of 65 to have it.
Whether or not there are other members of a family with Alzheimer's disease, everyone risks developing the disease at some time. It is now known that there is a gene, which can affect this risk. This gene is found on chromosome 19 and it is responsible for the production of a protein called apolipoprotein E (ApoE). There are three main types of this protein, one of which (ApoE4), although uncommon, makes it more likely that Alzheimer's disease will occur. However, it does not cause the disease, but merely increases the likelihood (i.e. it is a socalled predisposition factor). For example, a person of 50, would have a 2 in 1,000 chance of developing Alzheimer's disease instead of the usual 1 in 1,000, but might never actually develop it. Only half of people with Alzheimer's disease have ApoE4 and not everyone with ApoE4 suffers from it.
Europe
Between 50 and 70 percent of all people with dementia are suffering from Alzheimer's disease - a degenerative disease, which slowly and progressively destroys brain cells. It is named after Aloïs Alzheimer, a German neurologist, who in 1907 first described the symptoms as well as the neuropathological features of Alzheimer's disease such as plaques and tangles in the brain. The disease affects memory and mental functioning (e.g. thinking and speaking, etc.), but can also lead to other problems such as confusion, changes of mood and disorientation in time and space.
About one person out of twenty over the age of 65 suffers from Alzheimer's disease and less than one person in a thousand under the age of 65. However, it is important to note that although people do tend to become forgetful as times goes on, the vast majority of people over 80 stay mentally alert. This means that although the likelihood of suffering from Alzheimer's disease increases with age, old age does not itself cause the disease. Nevertheless, recent evidence suggests that age related problems such as arteriosclerosis may be important contributing factors. Also, as people are now living longer than in the past, the number of people with Alzheimer's disease and other forms of dementia will most probably increase.
In an extremely limited number of families Alzheimer's disease is a dominant genetic disorder. Members of such families inherit from one of their parents the part of the DNA (the genetic make-up), which causes the disease. On average, half the children of an affected parent will develop the disease. For the members of such families who develop Alzheimer's disease, the age of onset tends to be relatively low, usually between 35 and 60. The onset is fairly constant within the family. A link between chromosome 21 and Alzheimer's disease has been discovered. As Down's syndrome is caused by an anomaly in this chromosome, many children with Down's syndrome will develop Alzheimer's disease if they reach middle age, although they may not display the full range of symptoms.
USA
More than five million older Americans are living with Alzheimer's disease or other dementias, a 10% increase in prevalence from just five years ago. The disease usually begins after age 65 and risk goes up with age. 2.4 million people aged from the ages of 75 to 84 years -- 19% of the all U.S. adults in this age range -- have Alzheimer's. Among Americans ages 85 and older, an estimated 42%, or 2.2 million people, are living with dementia. There are 300,000 Americans at ages 65 to 74 with Alzheimer's (2% of the U.S. population for this age range). There are approximately 500,000 Americans younger than 65 with Alzheimer's or another dementia. It is estimated that at least 200,000 of these people younger than 65 have early-onset Alzheimer's. The other early-onset dementia cases may be attributable to Lewy body disease, frontotemporal disease, normal pressure hydrocephalus, Parkinson's disease, or Creutzfeldt-Jakob. Deaths attributable to Alzheimer's disease increased 32.8% from 2000 to 2004. In contrast, deaths from heart disease, breast and prostate cancers and stroke all declined over the same period.
