Alzheimer's disease: learning from the past, looking to the future.

Our understanding on the pathophysiology and clinical aspects related to Alzheimer's Disease (AD) have been largely improved since the first case recorded in the medical literature in the beginning of the 20(th) century. Regarding the age of onset of AD, an important change seems to have happened in the last century: from several AD cases reported in middle aged and young adults in the first half of the 20(th) century, the age of onset of AD seems to have increased at the end of that century and the beginning of the 21(st) century. Since the 1-century-long time interval is very narrow to make a hypothesis on a genetic modification, it is possible that modifiable risk factors of AD played a role in increasing the age of onset of AD. Although the exact etiology of AD remains unknown, experts currently agree that it is multifactorial, being the result of complex interactions among genetic, environmental and lifestyle factors, such as physical activity, nutrition, and smoking. In the present article, we briefly discuss how lifestyle trends in the last century may have contributed to the increase in the age of onset of AD, and propose future directions for research on AD and lifestyle factors.