The brain function of Americans 70 and older appears to be improving, according to a study that found a smaller percentage of seniors with serious memory and language problems in 2002 than in 1993.
The finding, which researchers say is still preliminary, parallels an improvement in physical functioning among older Americans that is well documented.
"If this study is indeed confirmed and replicated, then it says that cognitive decline associated with aging is malleable," said Richard Suzman, director for behavioral and social research at the National Institute on Aging, which helped fund the study. "There may be interventions that can be brought to bear to accelerate the trend. It's potentially very good news."
Although the study does not mean that every individual will live healthier into old age, it does suggest that as a whole, people are functioning at a higher level for longer periods. That could mean that more people will be able to live independently later in life, said Suzman.
Researchers, however, cautioned that the aging of the baby boomers and the nationwide epi demic of obesity and diabetes will still bring a significant jump in the number of people with Alzheimer's disease over the next few decades. Both diabetes and obesity are risk factors for cardiovascular problems that can damage the brain.
Scientists are uncertain exactly what accounted for the improved cognitive health of the 2002 participants, but the study found that, on average, they had about one more year of formal education (12 vs. 11) than those in 1993, and had about $100,000 more in net worth. Using statistical analyses, the study found that those two factors could explain 43 percent of the difference in mental function. Education might help by enabling individuals to take on more mentally challenging jobs and leisure activities, thereby expanding brain capacity, while wealth might allow people to get better care for cardiovascular ailments.
The study, published online yesterday in the journal Alzheimer's & Dementia, compared results of mental function tests of more than 7,000 people over age 69 in 1993 with about the same number in 2002. More than 12 percent of test subjects in 1993 showed evidence of mental problems consistent with mild to severe dementia, compared with 8.7 percent in 2002. The researchers did not have access to clinical data that would have allowed them to test for dementia directly.
Extrapolated to the entire population, that would mean about 900,000 fewer people over 69 showed significant cognitive problems in 2002 than would have been expected based on the 1993 patterns, said Dr. Kenneth M. Langa, an associate professor of medicine at the University of Michigan, who was the study's lead author.
"We think that the brain health of [older] people in 2002 is better than the brain health in 1993," said Langa.
At least one local geriatrician is seeing that change in her patients.
"When they say 90 is the new 80, it's true," said Dr. Suzanne Salamon, associate chief of clinical geriatrics at Beth Israel Deaconess Medical Center. "I see 90-year-olds who are very active, going to lectures, enjoying life. We're seeing this a lot more."
However, there appears to be a downside to the trend. In the study, people who showed moderate to severe cognitive impairment in 2002 were more likely to die within two years than those with impairments in 1993, and this was especially true of those with more education. Langa and his colleagues suggest that education helps the brain function better despite accumulating damage, so the problems aren't evident until they are much more severe. As a result the decline to death appears more rapid. This supports findings in other studies of a protective "cognitive reserve" in some people.
Other scientists cautioned about generalizing too much from one study's results, until they are confirmed by other researchers. In addition, some questioned details of the methodology, particularly whether the study properly took into consideration age differences in the two populations and whether it is appropriate to predict a trend from testing at just two time periods.
"The data are highly limited for reaching the conclusion they have," said Dr. Denis Evans, a professor of medicine at Rush University Medical Center in Chicago who studies cognitive decline in old age. "I would hedge it."
Langa said the trend became even stronger when the research team controlled for the fact that the study population in 2002 was older than that in 1993. And, he said, a preliminary look at test results from seniors in 2004 and 2006 suggests the trend is continuing.
"We think the change is strong enough to hold even if there are some problems" with technical details of the study, Langa said.
The conclusions are also consistent with the findings of two previous studies, but contradict a third study that found no change using similar data.
The research builds on studies that found chronic physical disability had declined among people 65 and older - from more than 26 percent of the population in 1982, to 19 percent in 2004, Suzman said. Those studies measured seniors' ability to perform basic activities such as using the toilet, as well as activities with a mental component, such as talking on the telephone.
"That finding changed the view of [physical] aging to one over which society has some modest degree of control," said Suzman. He suggested that the current study, if confirmed and if the trend continues, might lead to a similar change in thinking about mental aging.
The researchers suggest that better management of heart disease risks, such as high blood pressure and high cholesterol, might help most people maintain brain function, but the study did not measure that. Other researchers have suggested that exercising, eating healthy food, and socializing may help keep the mind sharp.
"I can't make a specific medical recommendation from this study," Langa said, "but continuing to use your brain and staying connected to the world . . . seems to be important for maintaining your brain health."
Alice Dembner can be reached at firstname.lastname@example.org.