The U.S. government wants to have a cure for Alzheimer's ready to go by 2025, and is prepared to spend big money to get there. An ambitious new international study will begin testing an experimental drug intended to prevent the onset of Alzheimer's, in what could mark a huge shift in the way health experts approach the disease. Here, a brief guide to the big undertaking:

Why is Alzheimer's such a big deal?
The degenerative brain disease affects 5.4 million Americans every year, but that figure could climb as high as 8.7 million by the year 2030. Symptoms generally begin appearing in adults around age 50, but those as young as 45 can begin experiencing memory loss. The afflicted typically see a steep decline in mental functioning, including a loss of memory, perception, language, and cognitive skills. There is currently no cure, although a few medications can temporarily ease symptoms.

What is this study trying to accomplish, exactly?
Government and academic researchers will test an injectable drug called Crenezumab to see if it could prevent Alzheimer's in participants genetically assessed to have a "high risk." The massive $100 million trial will follow the lives of 300 participants, some as young as 30, over a five-year period — before they start showing symptoms. Most participants are members of one extended family in Colombia with a brain mutation that makes them susceptible to the disease, but unrelated individuals living in the U.S. will also be studied, says the Wall Street Journal

How does Crenezumab work?
Scientists still aren't sure what causes Alzheimer's. But one of the chief suspects is a "sticky gunk called beta-amyloid," says Lauran Neergaard at the Associated Press. Beta-amyloid clumps together to form a thick plaque that may clog the brain and kill its cells. Previous studies of anti-amyloid drugs have largely failed, but Crenezumab is designed to attack the formation of plaque from the beginning, and hopefully, slow Alzheimer's down.

Why is this study so important?
"No existing medications slow the course of the disease, and efforts to develop new drugs have been slow," says the Wall Street Journal. Major studies designed to tackle memory loss are, by nature, time consuming and expensive (researchers have to wait years for symptoms to develop). Nonetheless, experts are optimistic about the study's current trajectory. "Once the train leaves the station of degeneration, it might be too late to stop it," Dr. Reisa Sperling of Harvard medical School tells the Associated Press. "We need to define the critical window for intervention," which this experiment will help accomplish.

What can ordinary people do to slow Alzheimer's symptoms?
There are a few things people with a family history of Alzheimer's can do in the meantime, says Dr. Carl Cotman of the University of California, Irvine. The brain is like a muscle, and regular "exercise" can help slow down symptoms. Intellectual and social stimulation, for example, may help fight cognitive decline. Regular physical activity is also encouraged, and has been shown to increase blood flow in the arteries, which is important for brain health overall. Lastly, heart-healthy foods, like the omega-3 fatty acids found in fish, may help the brain stay alert and functional.

Sources: Associated Press, U.S. National Library of Medicine, U.S. News, Wall Street Journal