Delaying Autumn: Ongoing Research to Slow Age-Related Cognitive Decline

Timothy Salthouse, PhD

Brown-Forman Professor of Psychology, University of Virginia

This interview was conducted by Peter Cook on May 25, 2006.

Introduction

Aging, even in perfectly healthy individuals, impacts cognitive functioning. The cognitive results of aging are increasingly well catalogued, but the mechanisms for these changes are still not understood. Dr. Timothy Salthouse has devoted the last 30 years to exploring just these issues. “In my laboratory,” he says, “we’re trying to find out how cognitive performance varies as a function of age, and whether those relationships are independent across different cognitive variables.” The long-term goal, of course, is to find a way to fight the negative cognitive effects of aging.

Cognition and Aging — Moderators

In comparisons of people of different ages, cognitive ability is progressively lower with increased age. Dr. Salthouse has further found that some of those differences begin when people are in their 20s or late 30s; cognitive decline is not something that just emerges in seniors.

“We’ve been trying to find out what the moderators are,” Dr. Salthouse says. “Why, at age 60, are some people performing at a very high level—at least as high as the average young adult—and some performing at very low levels.” He and his team have looked at various factors: gender, amount of education, initial level of ability, amount of physical activity, amount of self-reported cognitive stimulation, and various personality characteristics. “We’ve tested as many possible moderators as we can think of, but we have yet to find any that significantly impact age-related trends in cognitive functioning.”

Effects of Aging on Cognition

According to Dr. Salthouse, “cognition requiring novel problem solving is most affected by aging. Transforming familiar material in unique ways, for example identifying novel patterns of letters, is the sort of ability that begins to decline with age in the 30s. However, knowledge you’ve acquired through experience, such as vocabulary, doesn’t decline at all, or at least not until well into the 60s or 70s.”

Causes

There are a number of hypotheses regarding the causes of cognitive decline with aging. Some scientists are pursuing behavioral explanations, looking for which aspects of the processing system are primarily responsible for decline. Candidates are: slower processing speed, reduced working memory, and inability to inhibit irrelevant information. Another level of analysis focuses on neurobiological substrates. Salient questions in this line of inquiry are: how functional are different regions of brain? Do the elderly have fewer operational synapses, and if so, in which systems? Are synapses formed as effectively in older adults as they are in the young? Is a decline in neurotransmitter activity linked with a decline in cognitive ability?

“I believe that the whole picture likely comprises quite a few of these different behavioral and neurobiological explanations,” Dr. Salthouse says. “I tend to believe that there are behavioral limitations having to do with control of cognitive operation, but that these are determined by neurobiological factors, primarily in the prefrontal cortex. What precipitates all these changes, however, is still an open question.”

Treatment

Outlook for treatment is currently rather grim. “Right now, there aren’t too many promising leads,” Dr. Salthouse says. “A number of people have high hopes for brain training, and even physical exercise, but the evidence for them isn’t strong. Of course, we don’t know of any harm attendant to mental or physical exercise, and it does seem that they improve immediate levels of functioning on the training activities, but we still don’t know whether these effects will last and result in a slower rate of age-related cognitive decline.” While mental and physical training aren’t silver bullets for cognitive decline, Dr. Salthouse still suggests that maintaining an active mind and body are likely relevant to mental health.

Further, “it’s not true that old dogs can’t learn new tricks,” he says. “You most certainly can learn new skills and improve old skills. There just isn’t any evidence that training generalizes across unrelated skill sets.”

As of yet, there have been no significant pharmacological advances pertaining to general cognitive decline. “There are different drug treatments being investigated,” Dr. Salthouse says. “The evidence for herbal treatments is very spotty, and while there’s even been some success in slowing the progression of dementia, that’s not normal cognitive aging. The underlying brain mechanisms in dementia or Alzheimer’s are probably different than those involved in normal cognitive aging; the behavioral results certainly are.” He further expounds that “the neurobiological markers of dementia are plaques and tangles. Some of these can be found in normal people, and some have speculated that normal aging may progress similarly to dementia on a neurobiological level, just less severe. All that’s still quite controversial.”

The Future

Dr. Salthouse’s continuing goal is to identify the cognitive changes that occur beginning in young adulthood and midlife, and to determine what characteristics are associated with minimizing those changes, whether these are related to lifestyle, diet, personality, genetic influences, or, as is likely, a mixture thereof. “I’d like to identify the factors associated with rapid or slower decline, and then, when we understand what’s going on, we might be able to intervene and keep people functioning at their highest level for as long as possible.”

Disclosure: Dr. Salthouse reports no affiliations with or financial interests in any organization that may pose a conflict of interest.

Source: http://www.ingentaconnect.com/content/bpl/cdir/2004/00000013/00000004/art00003