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Three Factors Tied to 13 Additional Dementia-Free Years
Key Takeaways
- Midlife vascular health was associated with nearly 13 more dementia-free years in a prospective U.S. cohort study.
- At age 55, healthier study participants averaged 30.1 additional years without dementia.
- Smoking, hypertension, and diabetes together sharply increased dementia risk and mortality.
Maintaining three key health factors during midlife -- normal blood pressure, no diabetes, and not smoking -- was associated with nearly 13 additional dementia-free years, a study of 12,000 people in the U.S. showed.
Individuals who met these criteria at age 55 lived an average 30.1 more years dementia-free, reported Josef Coresh, MD, PhD, of NYU Langone Health in New York City, and co-authors.
Conversely, those who smoked, had hypertension, and had diabetes at age 55 had dementia-free survival of only 17.5 years, Coresh and colleagues wrote in Neurology Open Access.
People with all three risk factors had a higher incidence of dementia (HR 2.69, 95% CI 1.94-3.73) and a higher incidence of dying before a dementia diagnosis (HR 5.61, 95% CI 4.67-6.74) compared with those who had no risk factors.
Overall, women lived longer without dementia than men at all risk levels. White participants had more years free of dementia than Black participants, and APOE4 carriers had shorter dementia-free survival than noncarriers.
"Our findings argue that people need to actively avert these factors in midlife as a strategy for preserving brain health for more than a decade," Coresh said in a statement. "Discovering new ways to delay dementia is crucial with 42% of Americans at risk for developing the condition at any time after age 55."
The findings were based on 12,409 participants in the prospective Atherosclerosis Risk in Communities (ARIC) study, which started in 1986 to evaluate midlife vascular risk factors and late-life dementia.
Previous research from the ARIC cohort suggested that 22% to 44% of dementia risk by age 80 could be attributed to three vascular risk factors measured in midlife and early late life, after accounting for risk factor concurrence and interactions.
Hypertension was defined as systolic blood pressure ≥130 mm Hg, diastolic blood pressure ≥80 mm Hg, or the use of blood pressure medication; diabetes as fasting glucose ≥126 mg/dL, non-fasting glucose ≥200 mg/dL, a physician's diagnosis, or the use of any diabetes medication; and current smoking was self-reported.
"Our study complements this important work by shifting focus from probability-based and attributable risk metrics to a time-based estimand -- dementia-free survival years, which quantifies the expected duration of life lived cognitively intact," Coresh and colleagues wrote.
"This outcome integrates two clinically relevant processes: incident dementia and death before dementia, therefore reflecting the competing risks that shape real-world aging trajectories," they pointed out. "In contrast to previous ARIC studies, this framework emphasizes how vascular health influences the balance between longevity and cognitive health over the life course."
In the current analysis, ARIC participants had a mean baseline age of 56 and 56% were women. Dementia was tracked through cognitive assessments, informant interviews, and continuous surveillance. Deaths without dementia were captured from multiple sources including the National Death Index.
Over a median follow-up of 26.3 years, 3,008 cases of dementia and 5,238 deaths without dementia were documented. Better vascular health was linked with longer dementia-free survival in a dose-response pattern.
"Several biologic pathways likely underlie our observed associations between vascular health and dementia-free survival, including chronic cerebrovascular injury, neuroinflammation triggered by vascular damages through hypertension and diabetes, and cumulative oxidative stress resulting from smoking," Coresh and colleagues wrote. "Together, these factors likely accelerate atherosclerosis, increase stroke risk, and may facilitate Alzheimer's disease pathology through promoting amyloid plaques and tau tangles."
The findings relied on one midlife assessment of risk factors, the researchers acknowledged. Dementia ascertainment may have differed between participants who attended recent visits and those who didn't. In addition, the study was observational and residual confounding may have influenced outcomes.
Zeyang Zheng†
Shanshan Yang
Zhongling Zhang
