Levene died in 1940, before the true significance of DNA became clear. Levene is known for his tetranucleotide hypothesis (formulated around 1910) which first proposed that DNA was made up of equal amounts of adenine, guanine, cytosine, and thymine.
Alzheimer's is not just a disease of old age. Younger-onset (also known as early-onset) Alzheimer's affects people younger than age 65.Up to 5 percent of the more than 5 million Americans with Alzheimerâs have younger-onset.eople 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.
For Alzheimer's disease, the incidence among people age 85 years and older is about 14 times that among people aged 65 to 69 years. Another study found that beginning at age 65, the risk of Alzheimer's disease increased by 23 percent per additional year of age.