Memory problems do not necessarily occur in the early period but will occur as DLB progresses. Attention, language, understanding and reasoning, ability to do arithmetic, logical thinking, and perceptions of space and time will be impaired. A DLB diagnosis is even more likely if the patient also experiences repeated falls, fainting, brief loss of consciousness, delusions, or is sensitive to neuroleptic drugs that are given to control hallucinations and other psychiatric symptoms. It is not presently clear how accurate the clinical diagnosis of DLB is. Nevertheless, other testing should be done to exclude other causes or illnesses such as Creutzfeldt Jakob's or vascular disease.
Depression is also a common cause of dementia-like symptoms.
However, in DLB they fluctuate frequently. DLB patients experience more depression than do Alzheimer's patients. Hallucinations are experienced by Alzheimer's patients in late stages, and by Parkinson's patients who take medications to improve movement and tremor. In DLB, hallucinations occur in early stages, and they are frequent, vivid and detailed. Life expectancy is slightly shorter for DLB than for Alzheimer's patients.