Alzheimer’s  is an age-related brain disease that gradually destroys a person’s memory and thinking skills and, eventually, even the ability to carry out the simplest tasks. Alzheimer’s is the most common cause of dementia , a loss of cognitive functioning and behavioral abilities so severe that it interferes with a person’s daily life and activities.
Some mild forgetfulness  is normal as people get older. But sometimes memory or other thinking problems are serious—they make it hard to do everyday things like driving, shopping, or even talking with a friend. For example, people with MCI  have memory or other thinking problems greater than normal for their age and education but can still function independently. MCI often, but not always, leads to Alzheimer’s dementia. Research is helping scientists better understand cognitive changes related to aging.