Diabetes, high blood pressure and smoking shape when the disease sets in
Adults who reached their mid-50s free of diabetes, high blood pressure and smoking lived roughly 13 more dementia-free years than peers who carried all three.
A study of 12,409 US adults published in the journal Neurology Open Access found those with none of the risk factors averaged 30.1 dementia-free years from age 55, against 17.5 years for those with all three.
The three factors the researchers tracked were diabetes, hypertension and current smoking.
The research drew on the Atherosclerosis Risk in Communities cohort, which has followed participants across four US communities since the late 1980s.
Researchers measured the risk factors when participants were about 56 years old on average, then followed them for a median of 26.3 years; 56 percent of the sample were women.
Compared with participants who had none of the factors, according to the study, those carrying all three were roughly 2.7 times as likely to develop dementia and 5.6 times as likely to die of another cause before dementia set in.
The time-based framing is the point clinicians can use, the authors suggested.
“That’s relatively easy for clinicians to discuss and patients to understand,” said Josef Coresh, the study’s senior author and founding director of the Optimal Aging Institute at the NYU Grossman School of Medicine.
Knowing how many additional “good years” a lifestyle change might buy, Coresh added, can motivate patients more than a percentage risk figure.
The authors cautioned that the study shows an association, not causation.
Researchers measured blood pressure, diabetes, smoking and other factors such as weight only once before the long follow-up, a window in which many variables could have shifted.
“View the results as an important estimate rather than the exact prediction for every individual,” said Sanjula Singh, an assistant professor of neurology at Harvard Medical School who was not involved in the research.
Singh put the share of dementia cases stemming from modifiable risk factors at about 45 percent.
Outcomes varied across groups.
Women stayed dementia-free slightly longer than men, and Black participants developed dementia a few years earlier than White participants.
Black participants also carried a higher burden of vascular risk factors, which the authors said likely contributes to the gap.
By age 85, only 7 percent of participants with all three factors remained dementia-free, compared with 35 percent of those with none.
The biological link runs through the circulatory system.
Damaged blood vessels, including those supplying the brain, cut the flow of oxygen and nutrients and raise the risk of stroke and small vessel disease, said Jacqui Hanley, head of research funding at Alzheimer's Research UK.
That leaves the brain more open to cognitive decline and dementia, said Hanley, who was not involved in the study.
For anyone weighing longevity against quality of life in later years, the findings sharpen a distinction that is drawing growing attention.
Andrew Freeman, a cardiologist and director of cardiovascular prevention and wellness at National Jewish Health in Denver, said the field is shifting toward health span over lifespan.
He described "the American curse" of working hard, saving, retiring and then facing heart attacks, strokes and dementia.
How people live "has the most profound impact," he said, at a scale no medication can match.
Freeman was not involved in the study.
