Senile dementia occurs as a result of degenerative brain cells. It is not as same as the senility that usually occurs in many elderly individuals. In the normal senility incidence, the gradual decline in brain function causes progressive memory loss and reduced mental abilities along with evident change in personality. Though the normal senility and senile dementia are not same, each of them are somewhat related to the old age.

So far, two major types of senile dementia have been identified depending on the specific cause behind the problem. One of these types is referred to as Alzheimer's type, which is due to generalized atrophy. Another type occurs due to vascular problems, leading to strokes. The term senile dementia is commonly used in reference with Alzheimer's disease.

Senile Dementia is not a single disease. It practically refers a group of different diseases such as Alzheimer's disease, Lewy Body disease, Parkinson's disease and vascular dementia . The most common form of senile dementia is Alzheimer's disease. In the case of Alzheimer's disease, the abnormal proteins or amyloid and brain atrophies are accumulated to form senile plaques. In addition to that the presence of abnormal filaments over neuron is common.

No one yet knows the exact reason of development of Alzheimer's disease. This is why there is no effective treatment for this problem. At the initial stage, Alzheimer's disease progresses very slowly, so it remains almost undetected at the earlier stages.

On the other hand, minor strokes are responsible for the development of multi-infarct dementia. It happens as a result of damages occurred in the small blood vessels in the brain. As the blood vessels get damaged, blood supply in the brain gets deprived. This significantly affects brain's normal function. Thyroid dysfunction, poor nutrition, alcoholism, drug poisoning, depression may also influence the incidence of senile dementia.