 Do you know the difference between dementia and Alzheimer's? Dementia refers to a broader umbrella term describing a number of brain disorders that are characterized mostly by loss of cognitive function, loss of memory and even difficulty in attention. Now Alzheimer's disease refers to the main form of dementia accounted for up to 75% of the cases globally. In fact over 50 million people live with Alzheimer's currently. It's also important to note that any small changes in memory as you get older is very different to the disease process of dementia.