What Causes Cognitive Decline? A Study Summary
Cognitive decline often begins subtly—forgetting words, failing to recognize new acquaintances, or leaving appliances on. While some individuals like atmospheric scientist James Lovelock remained mentally sharp well into their 90s, most people experience some cognitive deterioration with age. A new study from Ohio State University and the University of Michigan examined the root causes of both age-related and non-age-related cognitive decline.
Key Research Findings
The study, published in PLOS One in February 2023, analyzed data from over 7,000 participants born between 1931 and 1941, drawn from the larger Health and Retirement Study spanning 1996 to 2016. The researchers discovered that dementia accounts for only 41 percent of cognitive decline among aging Americans. Within dementia-related decline, Alzheimer’s disease represents 30-34 percent of cases, Lewy body dementia accounts for 4-8 percent, and cerebrovascular diseases comprise 1-3 percent.
More significantly, the study revealed that socioeconomic factors play the most crucial role in non-dementia-related cognitive decline. Education emerged as particularly important—not necessarily the number of years spent in school, but whether individuals completed college. College graduates showed slower cognitive decline compared to those without degrees.
Social and Lifestyle Factors
Marriage appears to protect cognitive function, with unmarried individuals performing worse cognitively than their married counterparts. Becoming widowed after age 54 caused particularly steep cognitive declines. Interestingly, having more children correlated with lower cognitive functioning in midlife but didn’t accelerate decline afterward.
The research confirmed expected lifestyle correlations: morbidly obese individuals and cigarette smokers experienced lower cognitive functioning and steeper declines. Chronic diseases including diabetes, heart disease, and psychiatric problems were also linked to cognitive deterioration. While vigorous exercise improved general cognitive functioning, it didn’t alter the overall trajectory of age-related decline.
The Wealth-Cognition Connection
Higher socioeconomic status—including greater wealth, income, and education—strongly correlated with better cognitive functioning at age 54 and slower subsequent decline. As neuropsychologist Karen D. Sullivan explained, quality early education contributes to “cognitive reserve” by building neural networks that can better withstand future neurodegeneration.
Unanswered Questions
Despite these significant findings, the researchers acknowledged substantial limitations. All controlled factors explained only 5.6 percent of population-level variation in cognitive decline rates, leaving the majority of differences unexplained.
Expert Recommendations for Brain Health
Given these research gaps, experts offer practical strategies for maintaining cognitive health:
Sleep and Circadian Rhythms: Dr. Cammy Benton, an integrative physician, emphasizes honoring natural sleep cycles—going to bed by 10 PM, rising with the sun, exercising in the morning, and taking evening walks.
Nutrition: Benton recommends “eating from the rainbow”—consuming diverse, brightly colored fruits and vegetables rich in phytonutrients, along with brain-supporting spices and herbs.
Botanical Supplements: Expert Donnie Yance suggests incorporating adaptogenic plants including water hyssop, saffron, Siberian ginseng, green tea, ginkgo, St. John’s wort, olive leaf, ginseng, rhodiola, red sage, grapes, horny goat weed, and ashwagandha.
Mental Engagement: Neurologist Dr. Robert Lowry advocates staying “mentally in the game of life”—continuously learning new skills, playing musical instruments, and traveling to challenge the brain.
The Bottom Line
While dementia represents less than half of cognitive decline cases, socioeconomic factors—particularly education and wealth—emerge as primary predictors of cognitive health. However, with over 94 percent of decline variation still unexplained, researchers emphasize that brains retain “remarkable capacity to adapt and change throughout our lives.” The key appears to be combining physical exercise, proper nutrition, adequate sleep, social connections, and continuous mental challenges to build cognitive resilience against age-related decline.
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