Recent groundbreaking research is reshaping our understanding of Alzheimer’s disease, revealing that its risk factors and links to cognitive decline emerge far earlier in life than previously believed—starting as young as 24. This article synthesizes key studies: one highlighting how Alzheimer’s-related risk factors correlate with cognitive function in adults aged 24–44, another exploring the role of personality traits in dementia risk, and expert guidelines emphasizing lifelong prevention. Together, they underscore that protecting brain health demands attention to both physical markers and psychological resilience from youth onward, with critical implications for global public health.
Picture this: A 28-year-old rushing to meet a work deadline, skipping lunch to cram in emails; a 35-year-old unwinding with a late-night cigarette and a few extra drinks after a stressful week; a 40-year-old feeling irritable and withdrawn after months of social isolation. These everyday moments—seemingly harmless, even trivial—might be more significant than we think. New science warns that the seeds of Alzheimer’s disease, long dismissed as an “old person’s woe,” could be quietly taking root in these very years, when we’re too busy building careers and lives to notice.
The Invisible Threat to Young Brains
In May 2025, a landmark study published in The Lancet Regional Health - Americas turned heads by focusing on a group rarely linked to Alzheimer’s: young and early-middle-aged adults. Its goal? To investigate whether known Alzheimer’s risk factors and blood-based biomarkers—biological clues in the blood—are already tied to cognitive function in people aged 24 to 44.
doi: 10.1016/j.lana.2025.101087.
The research drew on data from the “National Longitudinal Study of Adolescent to Adult Health” (Add Health), a massive ongoing project tracking thousands of Americans over decades. Specifically, it analyzed two waves of data: Wave IV (2008), which included participants aged 24–34, and Wave V (2016–2018), when those same individuals were 34–44.
Researchers measured a range of factors. One key metric was the CAIDE score, a tool that combines variables like age, education level, gender, blood pressure, body mass index (BMI), cholesterol levels, and physical activity to gauge dementia risk. They also looked at genetic factors, such as whether participants carried the APOE ε4 gene—a known risk factor for Alzheimer’s—and various blood biomarkers: total Tau protein (a protein linked to brain cell damage), neurofilament light chain (NfL, a marker of nerve cell injury), high-sensitivity C-reactive protein (hsCRP, a sign of inflammation), and several interleukins (proteins involved in the body’s immune response).
Figure : Among people aged 24-44, the more cardiovascular risk factors there are, the worse their memory and thinking abilities are
The findings were striking. Among 24–34-year-olds, higher CAIDE scores directly correlated with worse performance on cognitive tests. For example, every 1-point increase in the CAIDE score was associated with an average 0.03 standard deviation drop in scores on the reverse digit span test—a measure of working memory. By ages 34–44, the connections grew clearer: higher levels of total Tau protein were linked to weaker immediate word recall, while inflammatory markers like IL-6, IL-1β, and IL-8 were tied to lower scores across multiple cognitive tests.
These results—drawn from large samples (Wave IV analyzed 4,507 to 11,449 participants; Wave V, 529 to 1,121)—mark the first time scientists have systematically shown that Alzheimer’s risk factors and cognitive function are intertwined in healthy adults as young as 24.
Figure : Tau protein is associated with immediate word recall ability, and biomarkers of brain neural damage may affect memory in young people
Could a “Bad” Personality Raise Dementia Risk?
If young adulthood habits matter, what about personality? A 2024 study in Alzheimer's & Dementia explored this question, and its findings are equally thought-provoking.
doi: 10.1002/alz.13523.
Researchers used advanced statistical techniques—meta-analysis and Bayesian multilevel modeling—to comb through data from 8 independent studies, involving 44,531 participants (including 1,703 diagnosed with dementia). The participants’ average age at the start of the studies ranged from 49 to 81, and they were followed for 3.5 to 21 years.
The results? Certain personality traits were linked to a higher long-term risk of dementia. Emotional instability, a tendency toward negative emotions, and low levels of conscientiousness, extraversion, or positive affect all increased the odds of a dementia diagnosis later in life.
Figure: Multiple personality traits are associated with the risk of new dementia diagnosis, among which neuroticism and negative emotions increase the risk, while conscientiousness, extroversion and positive emotions reduce the risk
But here’s the twist: these personality traits didn’t directly cause visible brain damage. Autopsies of participants showed no consistent link between psychological traits and neuropathological changes (like amyloid plaques or tau tangles, the hallmarks of Alzheimer’s). Instead, the researchers suggest, personality may influence how well the brain compensates for underlying damage. For example, people high in conscientiousness—those who are organized, responsible, and goal-driven—seemed better at “hiding” early signs of brain decline, showing greater cognitive resilience.
Figure: As people age, individuals with high conscientiousness have a lower risk of dementia
What This Means for All of Us
The message is clear: Alzheimer’s isn’t a disease that suddenly strikes in old age. Its roots stretch back to young adulthood, and both physical health and psychological resilience play roles.
In 2024, the Lancet Commission on Dementia Prevention, Intervention, and Care reinforced this, identifying 14 modifiable risk factors that could prevent or delay up to 40% of global dementia cases. These include: low education in childhood, hearing loss, high blood pressure, smoking, obesity, depression, lack of exercise, diabetes, heavy drinking, traumatic brain injury, air pollution exposure, social isolation, high “bad” cholesterol (LDL), and untreated vision problems. Critically, the commission stressed that starting prevention in childhood yields the strongest results.
Schools can prioritize early education and hearing/vision screenings; workplaces can encourage physical activity and reduce stress; individuals can quit smoking, limit alcohol, and stay socially connected. Even small changes—like swapping a late-night binge-watch for a walk with friends—could add up over time.
References:
- Aiello AE, Momkus J, Stebbins RC, et al. Risk factors for Alzheimer's disease and cognitive function before middle age in a U.S. representative population-based study. Lancet Reg Health Am. 2025;45:101087.
- Beck ED, Yoneda T, James BD, et al. Personality predictors of dementia diagnosis and neuropathological burden: An individual participant data meta-analysis. Alzheimers Dement. 2024;20(3):1497-1514.
- Bartrés-Faz, D., Demnitz-King, H., Cabello-Toscano, M. et al. Psychological profiles associated with mental, cognitive and brain health in middle-aged and older adults. Nat. Mental Health 3, 92–103 (2025).