Greg O'Brien (left), with Colleen, Mary Catherine, Conor, and Brendan O'Brien, has been grappling with Alzheimer's disease for the last five years. Courtesy Greg O'Brien hide caption

itoggle caption Courtesy Greg O'Brien

When he was 59 years old, Greg O'Brien was diagnosed with early-onset Alzheimer's disease. Five years later, he is speaking publicly about his experience, even as his symptoms worsen. Courtesy of Greg O'Brien hide caption

itoggle caption Courtesy of Greg O'Brien

Marian Grunwald (from left), Earl Elfstrom and Verna Matheson bounced a balloon back and forth with nursing assistant Rick Pavlisich on Dec. 13, 2013, at an Ecumen nursing home in Chisago City, Minn. Glen Stubbe/Star Tribune, Minneapolis St. Paul hide caption

itoggle caption Glen Stubbe/Star Tribune, Minneapolis St. Paul

Antipsychotic drugs aren't necessary in the vast majority of dementia cases, gerontologists say. The pills can be stupefying and greatly raise the risk of falls — and hip fracture. iStockphoto hide caption

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A tangle of protein (green) in this scanning electron micrograph of a brain cell of an Alzheimer's patient lies within the cytoplasm (blue) of the cell. The tangle consists of clumps of a toxic form of tau. Thomas J. Deerinck/Corbis hide caption

itoggle caption Thomas J. Deerinck/Corbis

Loretta Jackson gently stretches the hands of her sister, Shirlene English, to aid physical rehabilitation after Shirlene's brain aneurysm and stroke. Andrew Nixon/Capital Public Radio hide caption

itoggle caption Andrew Nixon/Capital Public Radio

Rick and Marianne wash dishes together. She no longer remembers that he is her husband. Andrew Nixon/Capital Public Radio hide caption

itoggle caption Andrew Nixon/Capital Public Radio

An Indian schoolgirl dressed as Telugu Talli poses for the camera during a celebration in Hyderabad, home to a study that seems to show the onset of dementia is delayed for people who speak more than one language. Noah Seelam/AFP/Getty Images hide caption

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University of Florida researcher Jennifer Stamps administers the peanut butter sniff test to a volunteer. Jesse S. Jones/University of Florida hide caption

itoggle caption Jesse S. Jones/University of Florida

Stressed out? Who isn't? Stress can cause physical changes in the brain that may be linked to Alzheimer's. iStockphoto.com hide caption

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Depression is common among old people, affecting up to 25 percent. iStockphoto.com hide caption

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An older man performs exercises in Mumbai, India. Research suggests that moderate physical exercise may be the best way to keep our brains healthy as we age. Rajesh Kumar Singh/AP hide caption

itoggle caption Rajesh Kumar Singh/AP

A towel covers the face of a man in a geriatric day care facility of the German Red Cross at Villa Albrecht in Berlin. Carsten Koall/Getty Images hide caption

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