Summary: Findings of a new study suggest more research needs to be done to identify the major factors contributing to the rate of cognitive decline associated with aging.
A new analysis explores relative statistical associations between various life factors and cognitive decline in elderly Americans, highlighting gaps in knowledge needed to reduce cognitive decline. Hui Zheng of the Ohio State University, U.S., and colleagues present these findings in the open-access journal PLOS ONE on February 8, 2023.
Millions of elderly Americans experience cognitive decline. However, only about 41 percent of this decline can be statistically accounted for by dementia—abnormal decline caused by such conditions as Alzheimer’s disease, cerebrovascular disease, and Lewy body disease.
Prior research has identified many other factors that may also contribute to cognitive decline, from genetics to early life nutrition, but their relative impacts remain unclear.
To shed new light, Zheng and colleagues analyzed data from 7,068 American adults born between 1931 and 1941 who were part of a larger study—the Health and Retirement Study—that regularly measured their cognitive function from 1996 to 2016.
The study also collected extensive information on personal factors that could contribute to cognitive decline, such as socioeconomic factors, physical health measures, and behaviors including exercise and smoking.
Together, the many factors considered in the study statistically accounted for 38 percent of the variation between participants in their level of cognitive function at age 54. Among those factors, personal education, race, household wealth and income, occupation, level of depression, and parental education were the biggest statistical contributors to that population-level variation, with early life conditions and adult behaviors and diseases contributing less.
However, all of the considered factors accounted for only 5.6 percent of the variation in how participants’ cognitive function changed with age.
Unlike many prior studies, this study also distinguished between age-related cognitive decline and cognitive decline that is unrelated to getting older. Age accounted for 23 percent of the variation in how cognitive function changed from age 54 to 85, but the remaining 77 percent could not be statistically accounted for by the many factors considered.
These findings suggest that more research is needed to identify the major factors contributing to rate of cognitive decline, which could help inform medical treatments, policies, and equity-based strategies to slow decline.
Hui Zheng adds: “Adulthood socioeconomic conditions have a predominant role in shaping the level of cognitive functioning. Future research is urgently needed to discover the main determinants of the slope of decline to slow down the progression of cognitive impairment and dementia.”
Kathleen Cagney adds: “Understanding cognitive health, and cognitive decline, is paramount. We must take the long view, with attention to the timing and nature of life experiences, if we are to gain fundamental insights that can inform care and treatment.”
About this aging and cognitive decline research news
Author: Hanna Abdallah Source: PLOS Contact: Hanna Abdallah – PLOS Image: The image is in the public domain
Predictors of cognitive functioning trajectories among older Americans: A new investigation covering 20 years of age- and non-age-related cognitive change
Despite the extensive study of predictors of cognitive decline in older age, a key uncertainty is how much these predictors explain both the intercept and age- and non-age-related change in cognitive functioning (CF).
We examined the contribution of a broad range of life course determinants to CF trajectories. Data came from 7,068 participants in the 1996–2016 Health and Retirement Study. CF was measured as a summary score on a 27-point cognitive battery of items.
We estimated multilevel growth curve models to examine the CF trajectories in individuals ages 54–85. We found that the variation in CF level at age 54 was three times as much as the variation in age slope.
All the observed individual predictors explained 38% of the variation in CF at age 54. Personal education was the most important predictor (25%), followed by race, household wealth and income, parental education, occupation, and depression.
The contributions of activity limitations, chronic diseases, health behaviors (obesity, smoking, vigorous activity), childhood conditions (childhood health, nutrition, financial situation), gender, marital status, and religion were rather small (<5%). Even though the age slope varied with many adulthood factors, they only explained 5.6% of the between-person variation in age slope.
Moreover, age explained 23% of within-person variation in CF from age 54 to 85. The rest non-age-related within-person variation could not be explained by the observed time-varying factors.
These findings suggest that future research is urgently needed to discover the main determinants of the slope of cognitive decline to slow down the progression of cognitive impairment and dementia.