What Is The Disease?
Dementia is a broad term for all diseases characterized by a decline in memory, thinking, or behavior that affects a person’s ability to conduct activities of daily living. The most common type of dementia is Alzheimer’s disease that constitutes about 60% to 80% of all the dementia types. Other types include vascular dementia, which is more common in an elderly population; Lewy Body Disease and dementia associated with Parkinson’s disease. There are other less frequently seen dementias known as Frontotemporal Dementia, which is seen in younger age individual at or about 60 years of age and younger. While there are other types such as Creutzfeldt-Jakob disease and Normal Pressure Hydrocephalus, the majority of individuals fall within the first three types. Additionally, there is now evidence that there may be mixed types of dementia that may include symptoms of Alzheimer’s and Vascular dementia.
Dementia is caused by damage to the nerve cells (called “neurons”) in the brain that prevents them from functioning normally and sometimes hastening cell death.
The first neurons to malfunction and die are usually those in the brain. A healthy brain has about 100 million neurons each with long branching extensions enabling neurons to connect with each other. At these connections, called synapses, information flows in tiny bursts of chemicals that are released from transmitting neurons and are detected by receiving neurons. This allows signals to travel quickly through the brain’s circuits, creating the basis of memory, thoughts, sensations, movements and skills. Dementia interferes with the proper functioning of neurons and synapses.
Other changes in the brain believed to contribute to Alzheimer’s disease is the accumulation of a protein called “beta amyloid plaques” and an abnormal form of the protein called “tau,” which is inside of the neuron that is responsible for tau tangles. In Alzheimer’s disease, the transfer of information in the synapse begins to fail, the number of synapses is reduced and the neurons eventually die. The accumulation of beta amyloid interferes with neuron-to-neuron at synapses and the tau tangles block the transport of nutrients to the neuron contributing to cell death.
The neuronal changes may begin 20 or more years before symptoms appear. At the beginning of neuronal changes, the individual is able to function normally despite brain changes.
The brain is able to compensate to allow for more normal cognitive function until there is significant loss in neuron function and there is evidence of decline in thinking, memory and cognition. As the condition worsens, the neuron loss may be so great that memory loss occurs, confusion as well as anxiety and behavioral changes result, and the control of bodily functions becomes impaired.