What symptoms precede the onset of alzheimer's or parkinson's diseaase?

Early signs of: Dementia include short term memory loss, difficulty performing familiar tasks, changes in mood, behavior, or personality, word-finding difficulties, decreased judgment, loss of initiative, problems keeping track of things, disorientation to time or place, if you’re experiencing any of these symptoms or are concerned about a friend or relative, talk with your doctor about your concerns.

Different symptoms: Alzheimer's and parkinson's disease are quite different from each other. See these links for the 10 warning signs for each of these disorders. Alzheimer's: http://www.Alz.Org/alzheimers_disease_know_the_10_signs.Asp parkinson's: http://www.Parkinson.Org/parkinson-s-disease/pd-101/10-early-warning-signs-of-parkinson-s-disease.

For Parkinson's.....: Before overt physical symptoms begin, one can experience pre-motor parkinson's issues: the most reliably reported 4 are chronic constipation, chronic depression, anosmia (part or complete loss of smell--which also effects taste appreciation) & rbd. Rbd stands for rem behavior disorder. Rem  (dreaming stage sleep) can be accompanied by acting-out of dreams: talking, kicking, punching, running, etc.