Cognitive impairment among older Americans is declining

Feb 27 2008

Rates of cognitive impairment among older Americans are on the decline, according to a new study supported by the National Institutes of Health (NIH) comparing the cognitive health of older people in 1993 and 2002.

Higher levels of education were associated with better cognitive health.

Researchers said the findings will need to be explored further to see if they can be observed in other studies and to pinpoint factors influencing cognition, or the ability to think, learn, and remember. "These data suggest that we may be experiencing a shift in the cognitive health of older Americans," said Richard J. Hodes, M.D., director of the NIA. "Continuing to track trends will be critically important both for chronicling changes in brain health and for achieving a better understanding of factors that may play a role."

The report appears in Feb. 20, 2008, issue of Alzheimer's & Dementia (now online). The National Institute on Aging (NIA), part of the National Institutes of Health (NIH), and Harvard University, funded the study conducted by Kenneth M. Langa, M.D., Ph.D., and colleagues at the University of Michigan, University of Pennsylvania, and Group Health Cooperative of Puget Sound in Seattle. The National Institute of Mental Health (NIMH), also part of NIH, provided additional support.

The data come from the NIA-supported Health and Retirement Study (HRS), a national, longitudinal examination of health, retirement and economic conditions of more than 20,000 men and women over 50. Researchers tested memory and judgment of a large subset of HRS participants to determine cognitive status in two groups of people, those age 70 and older in 1993 and in 2002. The scientists then followed each group for two years to track death rates. They also looked at levels of education, income, and other factors in each group, finding that the 2002 participants were wealthier and had significantly higher levels of education, with 17 percent college-educated compared to 13 percent in 1993.

The analysis found:

• Cognitive impairment dropped from 12.2 percent in 1993 to 8.7 percent in 2002 among people 70 and older.
• Cognitive impairment was associated with a significantly higher risk of death in both cohorts.
• Education and financial status appeared overall to protect against developing cognitive impairment.
• Once older people with higher levels of education reached a threshold of moderate to severe cognitive impairment, they had an increased risk of death over the next 2 years compared to those with lower levels of education.

"Although the trend of improving cognitive health is consistent with chronic disability reductions since 1984 in those aged 65 and older, replication in other studies is essential," said Richard Suzman, Ph.D., director of NIA's Social and Behavioral Research Program, which oversees the HRS. "I'd like to see further analysis of how education, exercise, medications, cardiovascular health and lifestyle affect cognitive functioning."

The researchers suspect that improved treatment for stroke, heart disease, and vascular conditions from 1993 to 2002 might have been factors in the improvement. Further, they suggested, the results support the notion of cognitive reserve, which hypothesizes that the brains of more educated people may be better able to sustain greater damage from Alzheimer's disease or other pathology before clinical signs of impairment appear. In the study, the rate of cognitive impairment among people with higher levels of education was reduced, for both cohorts. The higher level of education, on average, in the 2002 cohort may be one important factor in the lower rate of cognitive impairment in 2002 compared to 1993.

The NIA leads the federal government effort conducting and supporting research on the biomedical and social and behavioral aspects of aging and the problems of older people, including Alzheimer's disease and age-related cognitive decline. For information on dementia and aging, please visit the NIA's Alzheimer's Disease Education and Referral (ADEAR) Center at www.nia.nih.gov/alzheimers, or call 1-800-438-4380. For more general information on research and aging, go to www.nia.nih.gov.

The National Institutes of Health (NIH) — The Nation's Medical Research Agency — includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.