August 6, 2026, 11:44 am | Read time: 6 minutes
Dementia is one of the greatest health challenges of our time. In Germany alone, an estimated 445,000 people are newly diagnosed each year. But what factors determine decades in advance how long a person remains mentally healthy? A new long-term study provides a clear answer, highlighting three modifiable risk factors–high blood pressure, diabetes, and smoking.
Three Risk Factors–and Up to 13 Fewer Years Without Dementia
During the follow-up, around 3,000 participants developed dementia. More than 5,200 died before developing dementia. The analysis showed a clear connection: The more of the three risk factors present in midlife, the shorter the time participants lived without dementia.
People without high blood pressure, diabetes, and smoking spent an average of about 30 years without dementia between the ages of 55 and 95. With one risk factor, it was about 26 years, with two about 21 years, and with all three risk factors, only about 18 years. Thus, there were about 13 dementia-free years between having no risk factors and having all three.
The risk of developing the disease also increased significantly. Participants with all three risk factors had nearly three times the risk of developing dementia during the study compared to those without these risk factors. At the same time, their risk of dying from other causes before developing dementia was more than five times higher.
Not Just the Risk–But Also the Years Without Dementia
Previous studies have already shown that high blood pressure, diabetes, and smoking can increase the risk of later dementia.1,2 However, the current study aimed to determine the impact of these risk factors on the number of dementia-free years.3 The results were published in the journal “Neurology.”
Researchers analyzed data from about 12,400 adults from the U.S. ARIC study (Atherosclerosis Risk in Communities). Only participants who were alive at age 55 and did not have dementia were included. At the start, researchers recorded three modifiable vascular risk factors: high blood pressure, diabetes, and current smoking. They then followed the participants for more than 26 years.
Using memory and cognitive tests, telephone interviews, surveys of relatives, and hospital and death records, they documented who developed dementia or died from another cause. Based on this, they calculated how many years participants lived without dementia between the ages of 55 and 95 on average.4
Women Had an Advantage in All Groups
The connection was also evident in the subgroups studied. Women lived longer without dementia than men, regardless of the number of risk factors. With all three risk factors, women spent about 18 years, and men about 17 years without dementia. Black participants achieved fewer dementia-free years than white participants. People with the APOE-ε4 gene variant, which increases Alzheimer’s risk, also lived shorter without dementia. However, the connection between the three risk factors and dementia-free years remained in all groups studied.
Why One Result Initially Seems Contradictory
At first glance, one finding seems inconsistent: By age 95, fewer participants with all three risk factors developed dementia than in the group without risk factors. However, the reason is not a lower dementia risk. Many people with high vascular burden died earlier from other diseases and did not reach the advanced age where dementia is particularly common. Therefore, researchers focused primarily on the number of dementia-free years.
Also of interest: These Dementia Risk Factors Already Show in 20-Year-Olds
Why These Results Are Encouraging
The results underscore that vascular health in midlife could play an important role in later brain health. The authors conclude that high blood pressure, diabetes, and smoking should be detected and treated as early as possible. This aligns with existing recommendations for preventing cardiovascular diseases.
People with higher vascular burden could particularly benefit from preventive measures. At the same time, researchers emphasize that differences between population groups cannot be explained solely by medical risk factors. Social and health conditions are also likely to play an important role.
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How Vascular Health Could Affect the Brain
Why high blood pressure, diabetes, and smoking are associated with fewer years without dementia is not answered by the study. However, researchers cite several possible explanations, mainly involving blood vessels.
High blood pressure and diabetes can damage the small blood vessels in the brain over many years. This results in poorer oxygen and nutrient supply to the brain. At the same time, inflammatory processes can be promoted, and the risk of strokes increased. According to the authors, these changes could contribute to faster damage to nerve cells and the development of dementia.
Smoking is also likely to burden the brain in several ways. Previous studies suggest that smoking promotes oxidative stress, creating aggressive oxygen compounds that can damage cells. Along with the effects of high blood pressure and diabetes, this could further damage the vessels and promote changes that also play a role in Alzheimer’s disease. These mechanisms were not directly investigated in the current study but serve as possible explanations for the observed connections.
How Reliable Are the Results?
The study is one of the largest and longest investigations on this topic. Dementia diagnoses were obtained using various methods and additionally reviewed by experts, making the results particularly robust.
Despite its strengths, the study also has some limitations. The three risk factors were recorded only once at the beginning of the study. Changes during the study–such as medication, quitting smoking, or a healthier lifestyle–could not be considered. According to the authors, the actual impact of a consistently high vascular burden might even be underestimated.
Also, dementia was not diagnosed in the same way for all participants. While some were regularly examined in person, researchers relied on telephone interviews or data from hospitals and death registers for others. As a result, individual dementia cases may have been identified with varying reliability.
Conflicts of Interest and Funding
The authors report no relevant conflicts of interest. The study was funded by several public research institutions, including the U.S. National Institutes of Health (NIH) and other government funding organizations in the U.S. and China. According to the authors, the funders had no influence on the study design, data analysis, manuscript preparation, or the decision to publish.
The researchers observed the participants over many years but did not intervene in their treatment. Therefore, it cannot be said with certainty that high blood pressure, diabetes, and smoking alone are responsible for the differences in dementia-free years. Other, not fully captured influences could also have played a role. The study shows correlations but does not allow conclusions about cause and effect.