Activities and Alzheimer's Disease: Cognitive Reserve Research

Importance of Research

Dementia is one of the most common and feared ailments of aging, affecting 24 million people worldwide. If personal lifestyle choices (e.g., engagement in intellectually-stimulating activities, physical activity, encouraging children and young adults to pursue advanced educational opportunities) or public policies such as compulsory educational levels could be shown to modify the likelihood of developing Alzheimer's disease or other dementias, the public would greatly benefit from fostering such behaviors, choices and experiences. Since there is no medical cure or preventive strategy for Alzheimer's disease, such lifestyle modifications may be the best hope for adults today to minimize the risk for dementia in their lifetime.

Research Challenges

As we have addressed in a recent article (Jones et al., 2011, in press JINS), the cognitive reserve hypothesis is difficult to study for a number of reasons:

• Full testing of the hypothesis requires in-vivo assessments of neuropathology, which were only developed in recent years and are not generally available for use in prospective epidemiological research studies.
• Indicators of cognitive reserve must be isolated from socioeconomic status. Some indicators of cognitive reserve overlap with indicators for socioeconomic status.
• Conceptual arguments and specialized statistical procedures are needed to isolate more broadly the effect of reserve in brain health from well-known socioeconomic status differences in health and aging.
• There are many reasonable alternative explanations for why there might be a statistical association but non-causal relationship between lifetime experience and dementia in later life.
  • Bias in mental testing. People with more education might be better prepared when confronted with mental status tests involving reading, writing and arithmetic used to screen for dementia or assess cognitive level in later life. Thus, it would appear that people with more education are less likely to develop dementia, but, in reality, it is simply a delay in diagnosis.
  • Reverse causality. People with a high IQ-through genetic luck or cultivated with an enriched early-life environment-may do well on screening and testing in late life, have a tendency to engage in intellectually-stimulating activities throughout life, and may be resistant to clinical dementia.
    

We need to know if the cognitive reserve theory is a fair reflection of reality. Adults have limited time to engage in health-promoting behaviors, and public resources must be directed toward the most promising interventions that produce the greatest benefits for society.

Research Findings

• Bias in mental testing is present, but does not sufficiently explain education group differences in cognitive testing. While educational attainment is associated with late-life cognitive function, this association is not due to measurement bias (Jones and Gallo, 2001 and 2002).
• Education protects against delirium. High educational attainment provides protection against delirium in older hospitalized patients (Jones, Yang et al., 2006). This finding is important because delirium, an acute cognitive disorder common among older adults, argues against the cognitive research theory's reverse causality explanation.
• Memory training boosts the use of appropriate strategies on memory tests. Training-related improvements in strategy use are further associated with less decline in memory and everyday functioning, as well as higher quality of life.

Current Research

• Cognitive reserve, delirium, and long-term cognitive decline: We are currently testing the cognitive reserve hypothesis as a large prospective epidemiologic study of delirium following elective surgery. This work is supported by a National Institutes of Health/National Institute on Aging program project grant.
• Lifespan behavioral genetic models of intelligence, cognitive activities, and Alzheimer's disease: This research, supported in part by an NIH/NIA conference grant on psychometrics in cognitive aging, is testing the alternative hypothesis that early-life IQ-and, specifically, the genetic effects for early-life IQ-is the source of common variance among IQ, late-life cognitive performance, and Alzheimer's disease. The study uses an existing database of elderly Swedish twins. Results will provide information about how modifidable lifetime risk for Alzheimer's may be versus the extent it may be predetermined by genetic factors.
• Memory training tasks lower the risk for cognitive impairment: Maintaining memory and preventing memory decline are important for the preservation of daily functioning and well-being among older adults. Memory training programs, based on the cognitive reserve theory, are designed to improve cognition and maintain levels of everyday function. Ongoing research on memory strategies uses information from a large, national study of health and retirement among older adults to characterize strategies as markers of cognitive reserve.