Dementia in people age 65 and older is most commonly caused by Alzheimer's disease, according to Mayo Clinic. Other causes include traumatic brain injuries, loss of nerve cells and Lewy bodies.
Dementia is an umbrella term that describes a decline in cognitive function, states Medical News Today. All forms of dementia are caused by a loss of brain cells and contribute to additional loss over time.
Alzheimer's disease causes clumps of protein to form in the brain, notes Mayo Clinic. Clumps formed by beta-amyloid proteins are known as plaques, and those formed from tau proteins are known as tangles. The disease develops gradually, reducing memory, language and spatial navigation abilities.
Lewy body dementia is caused by accumulations of alpha-synuclein protein, known as Lewy bodies, claims Mayo Clinic. Lewy bodies have been found in the brains of patients diagnosed with Alzheimer's and Parkinson's diseases. Patients with Lewy body dementia alternate between periods of clarity and lucidity, and they experience hallucinations, rigidity, and movement tremors.
Dementia in the elderly also results from injuries that damage or block the blood vessels in the brain, according to Medical News Today. Obstructions deprive parts of the brain from getting oxygen and causes brain cells to die in the deprived areas.