Alzheimer’s disease (AD) is a disease of the brain occurring mainly in the elderly, causing dementia.

Dementia is a general term used to refer to the loss of higher brain function such as memory and executive functions, such as thinking, learning, problem solving and planning. Albeit the commonest, Alzheimer’s is just one form of dementia, which particularly affects memory, judgment and reasoning. This disease is irreversible and progressive and there is currently no cure.

There are two physical features of Alzheimer’s disease: the formation of amyloid plaques and the presence of intracellular neurofibillary tangles, both occurring in the brain. The formation of amyloid plaques, abnormal clumps of beta-amyloid neuron fragments, is a multi-step process starting with the production of amyloid precursor protein (APP). Although normally broken down to harmless, soluble fragments, in Alzheimer’s Disease, specific enzymes break APP down to insoluble peptides which then form the thread-like structures called amyloid fibrils. The fibrils eventually clump to form the plaques. Researchers are also exploring the role of apolipoprotein-E (APO-E) as a control mechanism to plaque formation. When the protein tau is expressed in axons and becomes hyperphosphorylated, it greatly contributes to neurofibrillary tangle formation. These tangle formations are believed to be tightly related to the degree of dementia observed.

There are rare familiar forms of Alzheimer’s disease with a younger disease onset. Several genes have been identified in those families, all having to do with the metabolism of the ß-amyloid protein. Age is a significant risk factor, as the occurrence of the disease doubles every five years after the age of 65. Other risk factors may include head injuries, chronic hypertension and over expression of the APO E gene.

Although there are no known cures for Alzheimer’s disease, there are some treatments available which are intended to control the behavioral symptoms of the disease, such as anxiety and wandering, or to stabilize the deterioration caused by the disease. A number of medicines act to stabilize the condition by helping to maintain the level of acetylcholine in the brain, by inhibiting the enzyme that normally breaks it down. Acetylcholine is produced in the neurons primarily, but not exclusively, affected by Alzheimer’s disease.

Estimates suggest that as many as 10% of all people over the age of 65 and up to 50% of people over 85 suffer from Alzheimer’s disease (Alzheimer’s Association, US, 2006) The number of people affected by this disease is rising as people continue to live longer. As research continues in this area, a growing number of dementia syndromes are being identified. For example, intracellular accumulation of abnormal filaments of the tau protein is a common pathological feature of a diverse group of dementias and movement disorders termed “tauopathies” some of which used to be known as Fronto Temporal Dementia (FTD).Distinct isoforms of the tau protein expressed in different neuronal populations lead to the different types of tauopathies.