Measuring Memory Loss

More than a third of people over age seventy have some form of memory loss, according to a new study by a team of researchers from Duke and four other institutions.

While an estimated 3.4 million Americans have dementia, defined as a loss of the ability to function independently, the researchers estimate that another 5.4 million over age seventy have memory loss that disrupts their regular routine but is not severe enough to affect their ability to complete daily activities.

"Even among the people age seventy-one to seventy-nine, a sizable number had cognitive impairment. This is an age at which most people expect to have many productive years ahead," says Brenda Plassman, associate research professor of psychiatry at Duke and the study's lead author.

The researchers found that the frequency of memory loss without dementia increased with advancing age and with fewer years of education—similar to the trends seen in dementia. Nearly a quarter of those with memory loss without dementia also had a chronic medical condition such as diabetes or heart disease that appeared to be the cause of the cognitive impairment. The researchers speculate that this group is underdiagnosed because doctors are likely focusing on the primary health issue.

The study was conducted by researchers from Duke Medical Center, the University of Iowa, the University of Michigan, the University of Southern California, and the RAND Corporation. Their data, published in the Annals of Internal Medicine, are from the Aging, Demographics and Memory Study, which is part of a larger Health and Retirement Study led by the University of Michigan Institute for Social Research and paid for by the National Institute on Aging.