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Mental capabilities vary greatly between people as they age, but risk factors linked to cognitive decline explain very little of these differences, researchers say. 

In a new study, investigators from Ohio State University and the University of Michigan sought to determine what accounts for variations in cognitive health and the speed of decline over time. They used data from more than 7,000 participants in the US Health and Retirement Study and tracked cognitive functioning from age 54 to age 85 in study participants born between 1931 and 1941.

Key factors

Education was the most important predictor of cognitive functioning at age 54. It accounted for approximately 25% of the variation in mental abilities between people, results showed. Other factors that made a difference were race, household wealth and income, parental education, occupation and depression.

Yet at age 54, those factors explained only 38% of the variation in functioning among participants. And other factors such as chronic disease, health behaviors, gender, marital status and religion explained only about 5% of these differences.

Speed of decline

When examining the speed of cognitive decline over time, all of the factors studied accounted only for 5.6% of how fast it progressed from ages 54 and 85, the researchers reported. And genetic factors for Alzheimer’s disease, which the study did not analyze, are unlikely to explain this gap in understanding, they added. Other studies have shown that Alzheimer’s disease accounts for only about 41% of cognitive decline among older adults, lead author Hui Zheng, PhD, of Ohio State reported. 

Notably, the rate of cognitive decline among participants as they aged beyond their 50s was found to be more similar than the baseline of cognitive functioning found at age 54.

“From an intervention perspective, that suggests it is much more important to try to improve functioning at the baseline than trying to slow down the rate of decline,” Zheng said. 

The pervasiveness of cognitive decline in older adults makes it important to track predictive factors, Zheng said.

“But still, our study raises more questions than it answers,” he added. “We have a long way to go to understand the trajectories of cognitive functioning in older adults.”

Full findings were published in PLOS One.

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