The word "dementia" is an umbrella term used to describe a set of symptoms, including impairment in memory, reasoning, judgment, language and other thinking skills. Dementia usually begins gradually, worsens over time and impairs a person's abilities in work, social interactions and relationships. Often, memory loss that disrupts your life is one of the first or more-recognizable signs of dementia. Other early signs might include: Asking the same questions repeatedly Forgetting common words when speaking Mixing words up — saying "bed" instead of "table," for example Taking longer to complete familiar tasks, such as following a recipe Misplacing items in inappropriate places, such as putting a wallet in a kitchen drawer Getting lost while walking or driving in a familiar area Having changes in mood or behavior for no apparent reason Diseases that cause progressive damage to the brain — and consequently result in dementia — include: Alzheimer's disease, the most common cause of dementia Vascular dementia Frontotemporal dementia Lewy body dementia The disease process (pathology) of each of these conditions differs somewhat. Memory impairment isn't always the first sign, and the type of memory problems varies. It's also possible to have more than one type of dementia, known as mixed dementia.