Setting aside the notion of determining the number of individual animals on the planet for a moment, merely determining the number of species on the Earth is challenging. Science has only been able to offer estimates thus far, and totals vary greatly.
People who have early onset Alzheimer's may be in any stage of dementia â early stage, middle stage or late stage. The disease affects each person differently and symptoms will vary. If you are experiencing memory problems: 1  Have a comprehensive medical evaluation with a doctor who specializes in Alzheimer's disease.
1 Degenerative neurological diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease (a rare inherited disorder), and some types of multiple sclerosis.2  Vascular disorders, such as multi-infarct dementia, which is caused by multiple strokes in the brain. Degenerative neurological diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease (a rare inherited disorder), and some types of multiple sclerosis.