Dementia is a progressive disease, which means symptoms get worse over time. It can be categorized as “primary” — meaning the dementia itself is the main illness behind the symptoms — or as “secondary,” if the person’s dementia is because of a different disease.
Common types of primary dementia include Alzheimer’s disease, vascular dementia, Lewy body dementia, frontotemporal dementia and mixed dementia.
Alzheimer’s disease is the most common type of dementia, accounting for 60% to 80% of cases. In Alzheimer’s, cells called neurons have trouble communicating. The neurons are damaged in part due to a buildup of two proteins in the brain: tau and beta-amyloid. In people with Alzheimer’s, one of the first abilities affected is memory. Over time, people with Alzheimer’s have difficulties with everyday tasks, like cooking meals, driving and paying bills.
Vascular dementia is the second most common type. It occurs when there is an interruption of blood and oxygen to the brain, such as during a stroke. The abnormalities from vascular dementia can usually be seen with an MRI scan. The first symptoms tend to include difficulties with problem-solving, slowed thinking, loss of focus and organization.
Lewy body dementia is caused by abnormal deposits of a protein called alpha-synuclein, which forms clumps called Lewy bodies. The protein affects the chemicals that act as messengers in the brain. Symptoms of Lewy body dementia may include problems with thinking, movement, sleep and balance, as well as mood changes and constipation. (Parkinson’s disease dementia is a form of Lewy body dementia.)
Frontotemporal dementia results from damage to the frontal and temporal lobes of the brain, located behind the forehead and near the ears, respectively. This rare type of dementia can occur in younger people — 60% of those diagnosed are 45 to 64 years old. Symptoms often involve changes in behavior, movement, language and emotion.
Mixed dementia is when a person has more than one type of dementia at once. This type is often uncovered after a person has died; typically, during life, they’ll have been diagnosed with just one type of dementia and the second was unrecognized. People over 80 are more likely to have mixed dementia and experience a faster decline than those with only one type.
