Alzheimer's disease

Alzheimer's disease (AD), also called Alzheimer disease or simply Alzheimer's, is the most common cause of dementia, afflicting 24 million people worldwide. Alzheimer's is a degenerative and terminal disease for which there is currently no known cure. In its most common form, it occurs in people over 65 years old although a less-prevalent early-onset form also exists. The disease can begin many years before it is eventually diagnosed. In its early stages, short-term memory loss is the most common symptom, often initially thought to be caused by aging or stress by the sufferer. Later symptoms include confusion, anger, mood swings, language breakdown, long-term memory loss, and the general withdrawal of the sufferer as his or her senses decline. Gradually the sufferer loses minor, and then major bodily functions, until death occurs. Although the symptoms are common, each individual experiences the symptoms in unique ways. The duration of the disease is estimated as being between 5 and 20 years.

The symptoms of Alzheimer's disease are generally reported to a physician when memory-loss causes concern, and on suspecting Alzheimer’s disease, the physician or healthcare specialists will confirm the diagnosis with a behavioral assessment and cognitive tests, often followed by a brain scan.

The cause and progression of Alzheimer's disease is not well understood, but is associated with plaques and tangles in the brain.Possible causes and potential cures of the disease have been conjectured, with varying evidence supporting each claim. No treatment has been found to stop or reverse the disease, and it is not known whether current treatments slow the progression, or simply manage the symptoms. Many preventative measures have been suggested for Alzheimer's disease, but their value is unproven in reducing the course and severity of the disease. Mental stimulation, exercise and a balanced diet are often recommended, both as a possible prevention and as a sensible way of managing the disease.

Due to the incurable and degenerative nature of the disease, care-management of Alzheimer's is essential. The role of the main caregiver is often taken by the spouse or a close relative.[11] Caregivers may themselves suffer from stress, over-work, depression, and being physically hit or struck.


Causes

Most cases of Alzheimer's disease do not exhibit familial inheritance. At least 80% of sporadic AD cases involve genetic risk factors. Inheritance of the ε4 allele of the apolipoprotein E (ApoE) gene is regarded as a risk factor for development of up to 50% of late-onset sporadic Alzheimer's. The presence of this gene allele along with infection by Herpes simplex virus type 1 (HSV-1) further increases the risk of Alzheimer's disease. Several viral-host interactions are postulated, most relating to HSV-1’s targeting of Alzheimer’s susceptibility genes.[42][43] Genetic experts agree that there are other risk and protective factor genes that influence the development of late onset Alzheimer's disease. Over 400 genes have been tested for association with late-onset sporadic AD.

Five to ten percent of AD cases involve a clear familial pattern of inheritance in which the patient has at least two first-degree relatives with a history of AD. These cases often have an early age of onset (usually younger than sixty years). Nearly 200 different mutations in the presenilin-1 or presenilin-2 genes have been documented in over 500 families. Mutations of presenilin 1 (PS1) lead to the most aggressive form of familial Alzheimer's disease. Over twenty different mutations in the amyloid precursor protein (APP) gene on chromosome 21 can also cause early onset of the disease. The presenilins have been identified as essential components of the proteolytic processing machinery that produces beta amyloid peptides through cleavage of APP. Most mutations in the APP and presenilin genes increase the production of a small protein (peptide) called Abeta42, the main component of senile plaques in brains of AD patients.
Prevention
At present contradictory results in global studies, incapacity to prove causal relationships between risk factors and the disease, and possible secondary effects indicate a lack of specific measures to prevent or delay the onset of AD.[93] Different epidemiological studies have proposed relationships between certain modifiable factors, such as diet, cardiovascular risk, pharmaceutical products, or intellectual activities among others, and a population's likelihood of developing AD. Only further research, including clinical trials, will reveal whether, in fact, these factors can help to prevent AD.

The components of a Mediterranean diet, which include fruit and vegetables, bread, wheat and other cereals, olive oil, fish, and red wine, may all individually or together reduce the risk and course of Alzheimer's disease. Vitamins E, B, and C, or folic acid have appeared to be related to a reduced risk of AD, but other studies indicate that they do not have any significant effect on the onset or course of the disease, while at the same time may have important secondary effects in conjunction with other therapies. Curcumin in curry has shown some effectiveness in preventing brain damage in mouse models.

Although cardiovascular risk factors, such as hypercholesterolemia, hypertension, diabetes, and smoking, are associated with a higher risk of onset and course of AD, statins, which are cholesterol lowering drugs, have not been effective in preventing or improving the course of the disease. However long-term usage of non-steroidal anti-inflammatory drug (NSAIDs), is associated with a reduced likelihood of developing AD in some individuals. Other pharmaceutical therapies such as female hormone replacement therapy are no longer thought to prevent dementia, while a 2007 systematic review concluded that there was inconsistent and unconvincing evidence that ginkgo has any positive effect on dementia or cognitive impairment.

Intellectual activities such as playing chess, completing crossword puzzles or regular social interaction, may also delay the onset or reduce the severity of Alzheimer's disease. Bilingualism is also related to a later onset of Alzheimer.