A lot of confusion arises in making the distinction between dementia and Alzheimer since the two terms are often used interchangeably. Dementia and Alzheimer are different but still closely related to each other. Dementia describes the symptoms that occur when the brain is affected by specific diseases and Alzheimer is the most common type of dementia accounting for more than 60% of all dementias. Alzheimer's is a gradually progressive form of dementia.