Researchers at the University of Hawaii in Honolulu found about half of the people diagnosed with Alzheimer's may in fact have other forms of dementia caused by tissue damage.
The research involved brain autopsies on about 400 men. It found that it may be harder than previously thought to identify the source of dementia while a patient is still alive.
The researchers will present their findings at annual meeting of the American Academy of Neurology in April.
An important note: The findings are still preliminary and have yet to be examined by other experts in the field.