What's the Difference Between Alzheimer's and Dementia?

The terms are often used interchangeably, but they’re not the same.

• Alzheimer’s disease. Alzheimer's occurs when nerve cells in the brain are damaged or destroyed. Abnormal structures known as plaques (deposits of sticky protein fragments called beta-amyloid that accumulate in the space between the nerve cells) and tangles (twisted fibers of a protein called tau that build up inside brain cells) develop, and they might be the cause of the damage. The damage affects thinking, learning and remembering. Alzheimer’s disease can also cause disorientation and mood and behavior changes.
• Vascular dementia. After Alzheimer's disease, the most common cause of dementia is blocked or reduced blood flow to parts of the brain, often caused by a stroke. Signs and symptoms of vascular dementia typically come on suddenly and progress in clear stages. They can include aggression, hallucinations, paranoia and fluctuating mood. People with high blood pressure, diabetes or high cholesterol are more likely to develop this.
• Lewy body dementia. The third most common cause of dementia is thought to occur when the brain has trouble processing a protein, alpha-synuclein, that is widely present. Deposits of the protein form; they are known as Lewy bodies. Visual hallucinations and delusions, along with confusion and loss of thinking skills, are common. Problems with normal movement can also happen.
• Frontotemporal dementia. In this group of conditions (there are several subtypes), the frontal lobe of the brain (located behind the forehead) and the temporal lobe (located behind the ears) shrink over time, with ongoing nerve cell loss. It often begins before age 65, and sometimes even in the 20s. About a third of these cases are inherited. Problems with the brain protein tau and another protein known as TDP43 are suspected causes. Different subtypes cause different symptoms.
• Parkinson's dementia. Experts believe the same problems with the brain protein involved in Lewy body dementia are at play in Parkinson's dementia. Eventually, most people with Parkinson’s disease will develop Parkinson's dementia. It can involve hallucinations and mood changes, including apathy.
• Creutzfeldt-Jakob disease. This is a rare and rapidly fatal brain disorder in which spongy holes form in the brain tissue. The cause appears to be abnormal, infectious versions of a type of protein called a prion. It typically begins at around age 60. In addition to memory and cognitive problems and mood changes, it can cause lack of coordination, visual disturbances and involuntary movements.