The Brain-Health Connection: What Science Reveals About Cognitive Decline

A series of recent studies and scientific statements have examined the relationship between vascular health, cognitive function, and dementia risk, covering topics from carotid artery procedures to early-life risk factors and driving behavior in older adults. The findings, presented at medical conferences and published in peer-reviewed journals, offer a range of data points without establishing definitive conclusions on several questions.

Carotid Artery Procedures and Cognitive Function

A substudy of the CREST-2 trial presented preliminary findings at the American Stroke Association's International Stroke Conference 2026. The study compared cognitive outcomes among individuals with severe asymptomatic carotid artery blockage (greater than 70% stenosis) who were randomly assigned to intensive medical management alone, intensive management combined with carotid endarterectomy (plaque removal), or intensive management plus stenting.

Key Findings

• Over an average follow-up of 2.8 years, the substudy found no significant difference in thinking or memory skills among the treatment groups.
• This finding held true even for participants with the lowest initial cognitive function.
• Cognitive decline was observed in participants who experienced a stroke during the study, which validated the cognitive testing methods.
• A 2021 study had previously suggested a potential link between revascularization and improved cognitive function in patients with severe carotid stenosis.

Limitations

• Cognitive tests were conducted over the phone, restricting assessment of visuo-spatial skills and a full range of executive functions.
• Only English-speaking patients were included, which may limit generalizability.
• The research has not yet been peer-reviewed; findings are considered preliminary until published as a full manuscript.
• The study could not definitively determine if reduced blood flow is the sole cause of cognitive decline in carotid artery disease.

Commentary

"There should be no expectation of cognitive improvement after these treatments."
— Study lead author Ronald M. Lazar, Ph.D.

Mitchell Elkind, M.D., Chief Science Officer for Brain Health and Stroke at the American Heart Association (AHA), noted that while carotid revascularization benefits stroke reduction, it may not be sufficient to address complex cognitive decline pathways such as inflammation or neurodegeneration, and called for more research.

AHA Scientific Statement on Lifelong Brain Health

The AHA published a scientific statement titled "Brain Health Across the Life Span: A Framework for Future Studies" in the journal Stroke on April 28, 2026. The statement synthesizes research indicating that brain health is shaped over a lifetime by psychological, environmental, lifestyle, and social factors.

Demographic Context

• The U.S. population aged 65 and older is projected to grow from 58 million in 2022 to 82 million by 2050 (a 42% increase).
• Globally, the population aged 65 and older is expected to exceed 2 billion by 2050.
• Stroke is the fourth leading cause of death in the U.S. as of 2026 AHA statistics.
• More than half of stroke survivors develop cognitive impairment within one year, and up to one-third may develop dementia within five years.

Risk Factors Identified

• Mental health: Chronic stress, depression, and anxiety can cause physiological changes (inflammation, cell loss) that increase risk of memory loss, dementia, and stroke. Early-life depressive symptoms correlate with a twofold or greater increase in dementia risk. Remission rates for current depression treatments range from 30% to 50%.
• Adverse childhood experiences (ACEs): 17.3% of U.S. adults report four or more ACEs (abuse, neglect, or household dysfunction), which are linked to higher risk of learning difficulties, mental health conditions, and later cognitive decline.
• Chronic inflammation: Early-life inflammation from infection or stress may impair brain development; in adulthood, it is linked to Alzheimer's and Parkinson's disease.
• Gut microbiome: Healthy gut bacteria support brain protection; disruption (dysbiosis) is associated with neurodegenerative conditions. High-fiber diets promote short-chain fatty acid production, supporting blood-brain barrier integrity.
• Obesity: Excess weight can increase inflammation and damage blood vessels, harming cognitive function at all ages.
• Sleep: Adequate sleep supports brain development and memory; poor sleep or sleep apnea increases inflammation and risk of cognitive decline, and is linked to beta-amyloid and tau accumulation and altered cerebral blood flow.
• Social drivers: Lower socioeconomic status, limited education, and reduced access to healthy food, healthcare, and housing correlate with higher risk of cognitive decline.
• Environmental exposures: Air pollution, heavy metals, microplastics, and wildfire particulate matter can damage the brain via inflammation and vascular harm. Chronic exposure to PM2.5 is associated with dementia risk (hazard ratio 1.04 per 2 µg/m³). Prenatal NO2 exposure was associated with a decrease of 0.68 points in global psychomotor development scores per 10 µg/m³ increase. Approximately 26% of disability from ischemic stroke in adults is linked to air pollution.
• Early-life infections and chronic pediatric conditions: Congenital heart disease, sickle cell anemia, moyamoya, obesity, and infection-related stroke risks can affect brain development.

Recommendations

The statement recommends healthy lifestyle behaviors including regular physical activity, blood pressure and cholesterol control, healthy sleep, not smoking, stress management, and a Mediterranean-style diet rich in fiber and fermented foods. It also recommends reducing alcohol and substance use, increasing social support, and alleviating financial stress.

The AHA and Paul G. Allen Frontiers Group have created the AHA-Allen Initiative in Brain Health and Cognitive Impairment to address the growing burden.

Early-Life Risk Factors for Dementia

A review of research published in 2023 and 2024 examines risk factors for dementia that may originate before birth or in young adulthood.

Birth Factors (2023 Study)

A study by researchers in Sweden and the Czech Republic identified birth factors associated with slightly increased dementia risk:

• Sharing the womb with a twin
• Shorter birth spacing
• Maternal age over 35

Young Adult Risk Factors (2024 Study)

A study by the Global Brain Health Institute (GBHI) in Ireland, with experts from 15 countries, focused on adults aged 18-39. Risk factors identified include:

• Excessive drinking
• Smoking
• Physical inactivity
• Social isolation
• Pollution exposure
• Traumatic brain injuries
• Hearing or vision loss
• Low education
• Obesity
• Diabetes
• Hypertension
• High LDL cholesterol
• Depression

Supporting Evidence

• Long-term studies cited show that cognitive ability at age 70 is correlated with cognitive ability at age 11, indicating differences may exist from childhood.
• Brain scan evidence suggests that some dementia-related changes are more closely linked to early-life exposures than to current lifestyle.

Recommendations

Researchers propose interventions at three levels:

• Individual: Public health campaigns and school education funded by taxes on alcohol and cigarettes.
• Community: Advisory councils of diverse young adults to liaise with local governments.
• National: A brain health charter to promote lifelong brain health.

Emerging Factors

The study acknowledges factors requiring further research, including ultra-processed foods, drug use, screen time, stress, and microplastics.

The 2024 research was published in The Lancet: Healthy Longevity.

Driving Habits and Cognitive Decline

Preliminary research presented at the American Stroke Association's International Stroke Conference 2026 indicates that changes in older adults' driving habits may serve as early indicators of cognitive decline and dementia.

Study Design

• 220 adults aged 65 and older were followed for over five years.
• Researchers tracked driving behaviors using in-vehicle sensors.
• Brain imaging measured white matter hyperintensities (areas of brain damage due to reduced blood flow).
• Initially, all participants were free of dementia.

Key Findings

• Over the follow-up period, 17% of participants developed cognitive impairment, predominantly Alzheimer's disease.
• Participants with increased white matter hyperintensities drove less, made fewer trips, followed more repetitive routes, and committed more driving errors.
• These patterns were particularly noticeable in individuals who subsequently developed cognitive impairment.
• White matter damage in the posterior part of the brain (critical for visual processing and movement coordination) showed the strongest correlation with unsafe driving practices and elevated crash risk.
• Adults taking blood pressure medications, especially ACE inhibitors, demonstrated a lower likelihood of risky driving behaviors. This effect was observed even in the presence of brain damage and independent of whether blood pressure was at target levels.

Commentary

"Monitoring driving behavior with in-vehicle data loggers could assist in identifying older adults at higher risk for unsafe driving, loss of independence, and cognitive issues."
— Study author Dr. Chia-Ling Phuah

Dr. Nada El Husseini, not involved in the study, highlighted the finding regarding ACE inhibitors' potential to mitigate driving impairment despite white matter disease and advocated for further investigation.

Limitations

• Small sample size.
• Participant pool was mostly white and college-educated, which may limit generalizability.
• Medication use was self-reported.
• Researchers stated that future, larger studies with more diverse participant groups are planned.