Dementia isn’t a specific disease. Instead, dementia describes a group of symptoms affecting memory, thinking and social abilities severely enough to interfere with daily functioning.
Though dementia generally involves memory loss, memory loss has different causes. So memory loss alone doesn’t mean you have dementia.
Alzheimer’s disease is the most common cause of progressive dementia in older adults, but there are a number of causes of dementia. Depending on the cause, some dementia symptoms can be reversed.
What Causes Dementia?
The most common causes of dementia include:
- Degenerative neurological diseases. These include Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and some types of multiple sclerosis. These diseases get worse over time.
- Vascular disorders. These are disorders that affect the blood circulation in your brain.
- Traumatic brain injuries caused by car accidents, falls, concussions, etc.
- Infections of the central nervous system. These include meningitis, HIV, and Creutzfeldt-Jakob disease.
- Long-time alcohol or drug use
- Certain types of hydrocephalus, a buildup of fluid in the brain
Types of Dementia
Types of dementias that progress and aren’t reversible include:
- Alzheimer’s disease. In people age 65 and older, Alzheimer’s disease is the most common cause of dementia.
Although the cause of Alzheimer’s disease isn’t known, plaques and tangles are often found in the brains of people with Alzheimer’s. Plaques are clumps of a protein called beta-amyloid, and tangles are fibrous tangles made up of tau protein.
Certain genetic factors might make it more likely that people will develop Alzheimer’s.
- Vascular dementia. This second most common type of dementia occurs as a result of damage to the vessels that supply blood to your brain. Blood vessel problems can be caused by stroke or other blood vessel conditions.
- Lewy body dementia. Lewy bodies are abnormal clumps of protein that have been found in the brains of people with Lewy body dementia, Alzheimer’s disease, and Parkinson’s disease. This is one of the more common types of progressive dementia.
- Frontotemporal dementia. This is a group of diseases characterized by the breakdown (degeneration) of nerve cells in the frontal and temporal lobes of the brain, the areas generally associated with personality, behavior, and language.
- Mixed dementia. Autopsy studies of the brains of people 80 and older who had dementia indicate that many had a combination of Alzheimer’s disease, vascular dementia, and Lewy body dementia. Studies are ongoing to determine how having mixed dementia affects symptoms and treatments.
- Huntington’s disease. Caused by a genetic mutation, this disease causes certain nerve cells in your brain and spinal cord to waste away. Signs and symptoms, including a severe decline in thinking (cognitive) skills, usually appear around age 30 or 40.
- Traumatic brain injury. This condition is caused by repetitive head trauma, such as experienced by boxers, football players or soldiers.
Depending on the part of the brain that’s injured, this condition can cause dementia signs and symptoms, such as depression, explosiveness, memory loss, uncoordinated movement and impaired speech, as well as slow movement, tremors, and rigidity (parkinsonism). Symptoms might not appear until years after the trauma.
- Creutzfeldt-Jakob disease. This rare brain disorder usually occurs in people without known risk factors. This condition might be due to an abnormal form of a protein. Creutzfeldt-Jakob disease can be inherited or caused by exposure to diseased brain or nervous system tissue. Signs and symptoms of this fatal condition usually appear around age 60.
- Parkinson’s disease. Many people with Parkinson’s disease eventually develop dementia symptoms (Parkinson’s disease dementia).