CHICAGO Older Americans are having less trouble with their memories, and it may be because they spent more time in school, U.S. researchers said on Wednesday.
They found the rate of cognitive impairment -- which includes a range of ills from significant memory loss to Alzheimer's disease -- fell 3.5 percentage points among people 70 and over between 1993 and 2002.
"We found a clear relationship. The more education people had, the better they performed on cognitive tests," said Dr. Ken Langa of the University of Michigan, whose study appears in the journal Alzheimer's & Dementia.
Langa said the research reinforces other studies that suggest people who do mentally challenging tasks early on build up a reserve of brain power that helps them withstand later injuries to the brain, such as a mini-stroke.
"Your brain is wired up differently. You can sustain more insults over your lifetime," Langa said in a telephone interview.
To test this, Langa and colleagues looked to see if there was a relationship between education and mental agility in older Americans.
They used data on 11,000 people from the Health and Retirement Study, a national survey of U.S. adults. The researchers compared data gathered in 1993 with data from 2002.
They found that in 2002, 8.7 percent of those aged 70 or older had cognitive impairment, down from 12.2 percent in 1993. "We think education is part of the story here," Langa said.
In 1993, people who were 70 or older on average had 11 years of education. By 2002, those 70 and older had 12 years of education. "That is a relatively significant increase in the level of education," he said.
They also found that older adults with more education who did develop cognitive problems were more likely to die within two years.
Langa said the thinking is that people who have more education have developed different brain circuits that have allowed them to continue functioning at a high level.
"Once you put it off as long as you can, you are more likely to have a quicker decline and death," he said.
Langa said the results may also reflect better cardiovascular health, which can reduce strokes or other injuries that affect brain function. He said rising rates of obesity and diabetes could offset those gains.
"Cardiovascular risks have a close link to brain health," he said.
Langa said people should exercise their bodies to protect their cardiovascular health, and exercise their brains with puzzles and books.
(Editing by Maggie Fox and Cynthia Osterman)