<unk>  <unk>  is a brain disease that slowly destroys a patient's memory and thinking skills and, eventually, the ability to carry out the simplest tasks. Memory problems are one of the first signs of<unk> . Patients may have trouble remembering things that happened recently or names of people they know. Over time, symptoms generally worsen; associated problems can include getting lost, repeating questions, and taking longer than normal to finish daily tasks. As the disease progresses, patients may have trouble learning new things, recognizing family and friends, and communicating. Eventually, they will require total care.<unk>  is the most common cause of dementia among older people. Dementia is a loss of thinking, remembering, and reasoning skills that interferes with a person's daily life and activities. Other causes of dementia include blood vessel disease in the brain (called vascular dementia), Parkinson's disease, frontotemporal dementia, and Lewy body dementia.
There are two types of<unk> : early onset and late onset.
In early onset<unk> , symptoms first appear before age 60. Early onset<unk>  is much less common than late onset. Early onset<unk>  tends to progress rapidly and can run in families. Several related genes have been identified.
Late onset<unk> , the more common form of the disease, develops in people age 60 and older. Late onset<unk>  may run in some families, but the role of genes in the development of the disorder is less clear.
Alzheimer's disease
Multi-infarct dementia
Dementia with Lewy bodies
Parkinson's disease
Pick's disease
Semantic dementia
Creutzfeldt-Jakob disease
Dementia