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

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.
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.
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.

Related Questions

Which symptoms differentiate Parkinson's disease from alzheimer's?

Several . The parkinson's patient will have tremors, stiffness, and gait issues, not seen in alzheimer's. Parkinson's dementia pts may have a rem sleep disorder, florid hallucinations, fluctuating levels of communication, and memory loss which can be helped by cueing. Alzheimer's pts reverse sleep/waking, get worse during the day, cannot incorporate memory items, and lose ability to learn new tasks. Read more...