There are a number of causes and risk factors of dementia, some of which are modifiable and others that are not. Generally speaking, dementia is caused by changes in or damage to the brain. The most common causes include Alzheimer’s disease, Parkinson’s disease, vascular dementia, Lewy body dementia, frontotemporal dementia, and severe head injury. Less common causes include Huntington’s disease, leukoencephalopathies, Creutzfeldt-Jakob disease, multiple-system atrophy, multiple sclerosis, amyotrophic lateral sclerosis, and various infections. Risk factors include age, family history, genetics, alcohol use, smoking, atherosclerosis, high cholesterol, high plasma homocysteine levels, mild cognitive impairment, and diabetes.
Alzheimer’s disease is the most common cause of dementia by far, a progressive brain disease that results in memory loss, cognitive impairment, and other brain-related symptoms. Sufferers of Parkinson’s disease may develop dementia further down the line, especially if he or she shows a high severity of motor symptoms, has a mild cognitive impairment and is of older age. Lewy body dementia often causes short-term memory loss, and also affects the chemicals in the brain that are responsible for movement, behavior, mood, and thinking.
After Alzheimer’s disease, strokes are the second most common cause of dementia, which often go hand in hand with vascular dementia. Many small strokes or one large stroke can lead to vascular dementia, as well as severe hardening of the arteries and long-term high blood pressure. Frontotemporal dementia primarily affects the brain’s frontal and temporal lobes, which impact language, behavior, and personality. Severe head injury or traumatic brain injury is the third most common cause of dementia in people below the age of 50, after infection and alcoholism.
Moving onto less common causes of dementia, Huntington’s disease affects an individual’s cognitive process, emotional state, and movement. It’s an inherited genetic disorder that sometimes causes dementia. Leukoencephalopathy involves the white matter of the brain, and the rare subtype of primary central nervous system lymphoma called lymphomatosis cerebri can cause dementia. Creutzfeldt-Jakob disease is a rare and fatal degenerative brain disorder that rapidly worsens over a short period of time and leads to dementia. Similarly, multiple-system atrophy is another rare degenerative neurological disorder that affects the body’s autonomic nervous system.
Multiple sclerosis and amyotrophic lateral sclerosis, or MS and ALS, are two more conditions that sometimes lead to dementia. In multiple sclerosis, the immune system attacks the central nervous system, namely the brain and the spinal cord. In amyotrophic lateral sclerosis, the nerve cells that control voluntary muscle movement are affected, which makes walking, talking, and chewing difficult. As for infections, pneumonia, urinary tract infections, oral herpes, spirochete infections, and various other bacterial infections have been known to cause dementia.
Out of all the risk factors for dementia, increasing age is by far the most significant one. Genetics and family history also play a role, though many individuals with a family history of dementia do not develop the disorder, and many individuals without a family history do go on to develop one type or another. Atherosclerosis refers to the buildup of plaque inside the arteries, such as fats, cholesterol, and other matter. Atherosclerosis is particularly a risk factor for vascular dementia. Homocysteine is a type of amino acid, so plasma homocysteine refers to the level of amino acid in the plasma. As it turns out, above-average levels of homocysteine in the blood is a strong risk factor for dementia, specifically vascular dementia and Alzheimer’s disease.