What Causes Alzheimer's?

Scientists don't know yet what causes Alzheimer's disease. Most agree it is probably triggered by a combination of age, genetics, environment, and lifestyle factors.

Though Alzheimer's is not an inevitable or normal part of aging, there is no question that growing older greatly increases the risk of developing the disease. At age 65, you have at least a one in 10 chance of developing Alzheimer's. The risk doubles every five years after that. At age 85, the risk for AD is one in two.

Scientists are beginning to uncover clues to genetic influences in early- and late-onset Alzheimer's. Many suspect that diet, fitness levels, and lifestyle factors that put you at risk for diabetes and heart disease may also influence whether you get AD.

What is early-onset Alzheimer's?

Early-onset Alzheimer's disease is a rare form of AD that strikes people between the ages of 30 and 65. It accounts for approximately 10 percent of all cases in the United States, according to the Alzheimer's Association. Approximately half of early-onset cases run in families and are linked to three rare genes that cause Alzheimer's.


“I really try not to hold on to negative feelings. But I am still angry at how many hoops I had to go through to get a diagnosis,” says Suzanna, who was diagnosed with early-onset Alzheimer's in 2007, when she was 53.

A retired health care executive, she first consulted her internist about “weird memory and language problems” right around her fiftieth birthday. “I then spent three years going from doctor to doctor, specialist to specialist, scary test to scary test,” she says.

“In some places, it's tough to find specialists. In Boston, where I live, you have medical specialists galore. Everyone I saw was a top expert in some part of the brain or body or nervous system. But none of them saw all of me or all my symptoms.”

Suzanna was treated at different points with anti-anxiety drugs, anti-depressants, and hormone therapy. A neurologist who suspected Lyme disease prescribed a course of antibiotics. She also underwent batteries of tests, which were time-consuming, distressing — and ultimately inconclusive.

Meanwhile, her symptoms got worse. “I was having trouble remembering things and saying things. There was one week when my secretary whispered to me something like, ‘You told me that twice. Are you okay?’ A few days later, I was talking to my son on the phone, trying to remind him to lock the door. I couldn't remember the word for door! I think I said something like ‘secure the entryway.’”

At that point, Suzanna called her neurologist and demanded an emergency appointment. “I said, ‘Okay, you know my symptoms. They don't fit depression or menopause or Lyme disease. What do they fit?’

“Unfortunately, the answer was Alzheimer's,” Suzanne says. “But knowing it let me get on with life!”

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