March 21, 2008
Memory loss and thinking problems are becoming less common among older Americans, according to a new national survey of seniors aged 70 and older. Though preliminary, the findings correlate with other studies showing that overall, seniors today tend to be more physically fit and suffer from less disability than earlier generations. Still, with the population as a whole growing older, millions of Americans will continue to suffer from Alzheimer's disease and related disorders in the coming years, making Alzheimer's a top priority for this and future generations.
The researchers, from the University of Michigan Health Center, found than over a 10-year period, from 1993 to 2002, the prevalence of mental impairment in seniors went down by 3.5 percentage points from 12.2 percent to 8.7 percent, in a sample of some 11,000 people. The difference represents hundreds of thousands of people.
Although the researchers don't know why the decrease occurred, they suggest the declines in memory problems may be due to better education, a more affluent society, and improvements in cardiovascular care that can benefit brain health. More and more people have stopped smoking and take measures to control blood pressure and lower cholesterol, all of which may help to preserve the brain.
In the study, seniors with more formal education and personal wealth were less likely to have cognitive problems. The researchers note earlier research showing that education may help to build a person's "cognitive reserve," or the ability to sustain more insults to their brain before significant thinking problems arise. Personal wealth may allow for improved access to health care.
Lead author Kenneth Langa, M.D., Ph.D., calls the findings good news for today's seniors, noting that the new data support recent theories of how brains can be protected and preserved. "From these results, we can say that brain health among older Americans seems to have improved in the decade studied, and that education and wealth may be a big piece of the puzzle," says Langa, an associate professor of internal medicine at the University of Michigan Medical Center.
"We know mental stimulation has an impact on the way a person's brain is 'wired,' and that education early in life likely helps build up a person's cognitive reserve. We also know cardiovascular health has a close link with brain health," Dr. Langa said. "So what we may be seeing here is the accumulated effects of better education and better cardiovascular prevention among the people who were over age 70 in 2002, compared with those who were over age 70 in 1993."
The research team's analysis, in fact, suggests that about 40 percent of the decrease in cognitive impairment over the decade was likely due to the increase in education levels and personal wealth between the two groups of seniors studied at the two time points.
Langa notes that school attendance requirements, high school graduation rates and college or technical school enrollment rates all increased during the years when the adults in the study were children and young adults. In 1990, 53 percent of people over age 65 had a high school diploma, but by 2003 that proportion had increased to 72 percent. The rates of college-educated older people also rose, from 11 percent to 17 percent.
In recent years, research has suggested that the more education a person receives early in life, the more his or her brain will be able to stay sharp later.
At the same time, the use of cholesterol-lowering drugs, blood pressure medications and other preventive cardiovascular medications and strategies increased dramatically in the 1990s. These factors may have helped protect seniors' brain function by decreasing the incidence of vascular dementia cognitive problems brought on by strokes and decreased blood flow to and within the brain due to "hardened" or clogged arteries.
Richard Suzman, Ph.D., director of the Social and Behavioral Research Program at the National Institute on Aging, which partially funded the study, notes that "the trend toward improved cognitive status is consistent with a dramatic decline in chronic disability among older Americans over the past two decades, especially in the areas of everyday function that depend on cognition. It will be important to pinpoint the influence of factors such as increased education, exercise, medications, cardiovascular health, and lifestyle to discover which ones contributed to this trend and to also replicate the findings in other studies."
The authors cautioned that they could not tell which patients had true dementia, which requires additional clinical information, or Alzheimer's disease, which can be positively identified only on autopsy.
Keeping the Brain Vital
While the new study shows a decline in memory problem prevalence over time, the researchers note that the gains made in the 1990's and early in this decade might be offset by other recent trends in health. The rate of type 2 diabetes, for instance, is increasing rapidly, and diabetes can damage the blood vessels, including those that feed the brain. Many middle-aged and younger people are also following unhealthy eating and exercise habits that can lead to obesity and high blood pressure, all risk factors for Alzheimer's disease.
Even if the proportion of older adults with cognitive problems keeps declining, the total number of older adults with dementia will likely increase significantly due to the huge increase in the size of the over-65 population as the Baby Boom generation enters older age in the coming decades.
"This demographic reality will continue to make combating Alzheimer's disease and other types of dementia a top public health priority," said Allison Rosen, M.D., Sc.D., assistant professor of internal medicine at the University of Michigan.
Meanwhile, they say, today's older Americans should not rest on their laurels but instead should be pursuing activities that can keep their minds sharp and their cardiovascular risk low. From crossword puzzles and volunteer activities to blood pressure medications for those who need them, today's seniors can work to boost their brain health now and prevent decline later.
"More and more studies suggest that walking and other types of physical activity are important for preventing cognitive and memory decline," said study co-author Eric Larson, M.D., M.P.H., executive director of the Group Health Center for Health Studies in Seattle, where he has led many studies of the relationship between physical activity and brain health.
"The evidence seems to be showing that staying mentally engaged with the world in any fashion reading, talking with friends, going to church, going to movies is also likely to help reduce your risk down the road," Dr. Langa said.
University of Michigan Health System.
Alzheimer's & Dementia: The Journal of the Alzheimer's Association.