Tuesday is World Alzheimer's Day. It's a reminder of all the people who are fighting the disease and how far we still have to go to find a cure.

New research finds the stages of impairment that may precede Alzheimer's disease can be accurately detected. That could lead to earlier intervention before the condition begins to block memory.

Scientists still don't know what causes Alzheimer's disease and there is no known cure. It is the most common type of dementia. Around 50 million are living with the disease. Most are older than 60, but younger people do suffer from it as well.

Alzheimer's affects parts of the brain that control thought, memory and language.