Alzheimer’s disease (AD) is a neurodegenerative disorder which makes a person lose their cognitive abilities, altering daily functioning and leading to various levels of physical and emotional stress. Here are 10 things you should know about Alzheimer's disease, according to healthline.com:   1. Alzheimer's disease is the most common form of dementia, affecting approximately 40 million people worldwide, including five million Americans. Find out more about Alzheimer's disease here.