Scientists know that age is the greatest risk factor for Alzheimer's disease, but aging alone doesn't explain why some people develop the condition while others do not. Genetics, lifestyle factors and environmental influences also appear to play a role. Researchers are working to understand how these factors interact in the brain, explains Nilüfer Ertekin-Taner, M.D., Ph.D., a neurologist and neuroscience chair at Mayo Clinic in Florida.