According to doctors, the number of diagnosed cases of younger people with Alzheimer's disease (AD) is increasing, striking people at the peak of their career and childrearing years.

"While most people are diagnosed in their 60s, 70s and 80s, an increasing number are being identified in their 40s and 50s," says Leonard Berg, M.D., chair of the Association's Medical & Scientific Advisory Board, who refers to younger cases as "young-onset" or "early-onset" AD. Various estimates place their proportion at anywhere from one to 10 percent of all people with AD -- or from 40,000 to 400,000 people in the U.S.

Young-onset AD is not a new phenomenon. It's been around long before Alois Alzheimer discovered the debilitating brain disease in 1906. But in recent years researchers have made dramatic progress in their understanding of the nature and symptoms of Alzheimer's disease, contributing to the increase in diagnosed young-onset AD.

"We have a much better idea of the clinical picture of the disease compared to just 10 years ago," says Dr. Berg. "Because we're able to make a more accurate clinical diagnosis of AD, we now recognize it more readily in younger patients." A definitive diagnosis of Alzheimer's disease can only be achieved through examining brain tissue during an autopsy. As diagnostic techniques have improved, more older people are being diagnosed, as well, says Berg.

Another reason for the rise in young-onset cases: increased public awareness of AD. "Alzheimer's disease was not exactly a hot topic 20 years ago," says Berg. "But today, AD ranks with cancer and heart disease in terms of awareness and concern for getting the illness."