Lewy body disease does not have clearly defined stages, and its progression is much less predictable than Alzheimer's disease, according to the Lewy Body Dementia Association. Duration of the neurological disorder ranges from two to 20 years, and symptoms vary in nature and severity from patient to patient.
Lewy body dementia covers dementia with Lewy bodies and Parkinson’s disease dementia, two related disorders, explains the Lewy Body Dementia Association. The brain undergoes the same biological changes in both diseases, but they have different symptoms in their early development. Patients diagnosed with either disorder exhibit similar symptoms as the diseases progress. Common symptoms include restless leg syndrome, sleep apnea, fluctuations in cognitive abilities and hallucinations.