Alzheimer's Disease

Alzheimer's Disease (AD) is a dementing illness characterized histologically by neuritic plaques and tangles accompanied by neuronal cell loss. Alzheimer's Disease is largely a disease of old age, so prevalence is likely to double by 2025 as the number of individuals aged over 65 years doubles.

Epidemiology and aetiology

Age is the strongest risk factor for alzheimer's disease. the prevelance aproximately doubles for every 5 year increase in age, at least until age 90 years. the incidence is also age-dependent, the incidence is similar in men and women but the prevalence is greater in woman, probably reflecting their greater longevity.

Genetics- Family history is a clear risk factor; the risk is about threefold greater in the first degree relatives of patients with AD.

Environmental factors-Although the aetiology of AD is multifactorial, studies of enviromental risk factors have been disappointing. some reports have suggested that the disease is associated with exposure to alumunium, alcohol, head injury of family history of psychiatric illness (particularly depression); others have suggested an inverse association with arthritis, smoking and education.

Pathogenesis

Plaques are relatively large extracellular structures that, in their mature form, contain a central condensed core of amyloid protein surrounded by a halo of degenerating neurities.

Neurofibrillary tangles-comprise massive accumulations of the microtubule-associated protein tau, an assential component of the neurocytoskeleton. Findings that tau is heavily phosphorylated and that microtubules are lost in AD have led to search for regulatory mechanisms of tau phosphorylation as possible causes.

Diagnostic criteria for alzheimer's disease
Probable Alzaheimer's Disease

- Dementia established by clinical examination and documented by mini-mental state examination or other standardized screening test

- deficits in two or more areas of cognition

- progressive worsening of memory and other cognitive functions

- No disturbance of consciousness
- Onset at 40-90 Years
- Absence of systemic disorders or other brain diseases that could account for the progressive deficits in memory and cognition.

Possible Alzaheimer's Disease
- Onset, presentation or clinical course different from that above but patient has no disorders sufficient to cause dementia
- Patient has a systemic or brain disorder sufficient to produce dementia, but this is not considered to be the cause of the dementia (source McKhaan G, Drachman D, Neurology, Page 34)