Seeking Signposts for Action in Alzheimer's Numbers

Biostatistician Ron Brookmeyer doesn't hesitate to use the word epidemic when discussing Alzheimer's. "This disease may not be what people in public health are usually thinking of when they use the word," he says. "It's not infectious; it's a chronic disease. There are demographic trends involved instead of transmission patterns. But it's a significant change in disease patterns that's going to present enormous challenges."

Brookmeyer, PhD, took his first peek at the numbers of Alzheimer's cases that might loom ahead for the United States and its health care system in 1998. That paper now ranks among the most highly cited from the American Journal of Public Health.

More recently, Brookmeyer worked with research associate Elizabeth Johnson to build on that model and create a worldwide forecast. There are an estimated 27 million cases of Alzheimer's today, according to their model; it predicts that the number of cases will quadruple within 50 years to more than 100 million. At that point, one of every 85 persons in the world could have Alzheimer's, with more than 40 percent of those cases in a late stage necessitating the highly expensive equivalent of nursing home care.

Preparing the forecast was a complex undertaking.

Baseline Alzheimer's numbers are surprisingly hard to come by, as it's not a reportable disease. In addition, diagnostic standards vary widely depending on what country and region is being considered.

Brookmeyer and Johnson eventually developed their own software so that they could adjust input data in ways that allowed them to ask a couple of strategic questions: What if public health and medicine succeeded in delaying the onset of the disease? What if its progression were delayed?

"As much as we want to hit a home run and come up with a cure, that might be asking too much," Brookmeyer says. "What we wanted to know is, what if we can slow the clock a little?"

The answers were startling—and encouraging. Even a one-year delay in onset would reduce the number of Alzheimer's cases in 2050 by 12 million. A two-year delay would reduce that burden by 23 million cases.

The picture is more complicated when it comes to delaying disease progression, but it remains positive. A two-year delay in progression could result in 5 million more cases of Alzheimer's in 2050. However, there will be 7 million fewer cases in the high-cost late-stage of the disease. This may sound like a contradiction, but it's a logical result of the competing risks experienced by older adults. Alzheimer's is not the only health issue these patients face, after all, and more of them will succumb to heart attacks or diabetes before they ever reach the late stage of a delayed Alzheimer's.

"That turns out to be the real take-home message here," Brookmeyer says. "Modest improvements like these can have a tremendous public health impact."