Experts say a significant percentage of people diagnosed with Alzheimer's disease suffer from something else. A study released this week underscored that message. Researchers in Honolulu autopsied the brains of 426 Japanese-American men who were residents of Hawaii, and who died at an average age of 87. Of those, 211 had been diagnosed with a dementia when they were alive, most commonly Alzheimer's disease. The study found that about half of the men diagnosed with Alzheimer's did not have sufficient numbers of the brain lesions characterizing that condition to support the diagnosis.