What causes Alzheimer’s disease? Our knowledge of cognitive decline just got even cloudier

COLUMBUS, Ohio — Cognitive decline becomes a bigger concern as people age, so studying the risk factors is a prime concern for researchers. While, scientist continue to make progress when it comes to treating illnesses like Alzheimer’s, a new study say we still have a long way to go. A team from The Ohio State University finds that factors commonly associated with cognitive decline don’t play as big of a role as previously thought, especially with regard to the variations in mental abilities between older people.

The team finds that socioeconomic status, education, and race — which are most commonly related to cognitive function — only explain 38 percent of the variations in cognitive abilities among Americans at age 54.

“There’s still a lot we don’t know about why cognitive functioning varies so much between older adults,” says Hui Zheng, lead author of the study and professor of sociology at Ohio State, in a university release. “More research is urgently needed to discover the main causes of how quickly cognitive functioning declines and how we can slow down its progression.”

Your education is a major factor during middle age

Zheng, along with Kathleen Cagney, a professor of sociology at the University of Michigan, and Yoonyoung Choi, a graduate student at Ohio State, conducted a study to address this. They analyzed data from 7,068 participants in the 1996-2016 Health and Retirement Study. The participants were born between 1931 and 1941, and the researchers measured their cognitive performance at age 54, keeping a close eye on how it declined until age 85.

This is a unique study in that it goes much deeper into a patient’s slow decline than previous ones. The researchers were able to achieve this by using a large sample size representative of the relevant population. They also followed people through their lives, allowing them to use a wide range of potential predictors of cognitive functioning, according to Zheng.

At age 54, the most important predictor was education. This explained around 25 percent of the differences between older people, according to their results. Race, household income or wealth, parental education, occupation, and depression followed. Surprisingly, chronic diseases, health behavior, gender, marital status, and religion only explained close to five percent of the group’s cognitive differences. The team also found that variations in cognitive functioning at age 54 was three times as much as the variation in how rapidly participants declined over the following few decades.

“We found that the rate of cognitive decline was much more similar between participants than the baseline of cognitive functioning we found at age 54,” Zheng says. “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.”

Alzheimer’s gene may have less influence than we thought

The team notes that they could not account for patients carrying the gene APOE4, the marker heavily implicated in Alzheimer’s disease onset — the most common form of dementia. However, there are studies that’ve shown that this marker may not link to Alzheimer’s as much as once thought. In fact, some have shown that it only accounts for 41 percent of cognitive decline among the elderly. Either way, more work is still necessary to get to the bottom of it, and hopefully the findings lead to better interventions for people who suffer from dementia.

“Cognitive decline is pervasive in older adults, even those without dementia, which is why it is important to study other predictors of cognitive functioning and decline,” Zheng concludes. “But still, our study raises more questions than it answers. We have a long way to go to understand the trajectories of cognitive functioning in older adults.”

The findings are published in the journal PLOS ONE.

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About the Author

Shyla Cadogan, RD

Shyla Cadogan is a DMV-Based acute care Registered Dietitian. She holds specialized interests in integrative nutrition and communicating nutrition concepts in a nuanced, approachable way.

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