Researchers found having normal blood pressure, no diabetes and not smoking all had a positive effect on dementia risk.
Avoiding three things in middle age is linked to 13 more years without dementia, experts have said.
Having normal blood pressure, no diabetes and not smoking from age 45 to 65 keeps dementia at bay for well over a decade, research suggests.
A team from NYU Langone Health in the US studied more than 12,000 people to examine three key things affecting dementia risk.
“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,” senior investigator Dr Josef Coresh, director of the Optimal Aging Institute at NYU Langone, said.
The study, published in the journal Neurology, looked at 12,409 people who were free of dementia when they were aged 55.
People were assessed for high blood pressure, diabetes and smoking, and followed for an average of 26 years.
During that time, 3,008 people developed dementia and 5,238 people died without developing dementia.
Those who had none of the three risk factors lived without developing dementia nearly 13 years longer than those who had all three.
From age 55, people with no diabetes, no high blood pressure and who did not smoke had an average of 30.1 more years free of dementia, the study found.
Meanwhile, those with one risk factor had an extra 26.3 years, those with two had 21 years, and those with three had just over 17 years
Previous studies have found that lifestyle choices, especially in midlife, can reduce the risk of developing dementia.
These include exercise, not smoking, watching alcohol intake and not being socially isolated.
The new study said: “Individuals with no midlife vascular risk factors lived an average of 13 more dementia-free survival years compared to those with three risk factors…
“Vascular risk factors – including diabetes, hypertension (high blood pressure) and smoking – are well-established contributors to dementia risk.
“These factors often emerge in midlife and exert lasting effects on neurodegenerative pathology, underscoring the critical importance of early identification and management.”
The study also found that, no matter how many risk factors they had, women lived longer without dementia than men, and white people had more dementia-free years than black people.
Reacting to the findings, Dr Jacqui Hanley, head of research funding at Alzheimer’s Research UK, said: “Rather than focusing only on the chances of developing dementia, this study asks a question that matters to people: how long can we expect to live free from dementia?
“This approach gives a meaningful picture of how midlife health may shape the number of years we spend living free from dementia, while also recognising that high blood pressure, diabetes and smoking are linked to a higher likelihood of dementia as well as a greater risk of dying earlier from other conditions.
“These findings emphasise why it’s so important to look after your heart health as well as your brain health.
“Alzheimer’s Research UK’s Think Brain Health campaign encourages everyone to take practical steps to do just that, including staying physically active, not smoking, and managing conditions such as high blood pressure and diabetes.
“While there is no guaranteed way to prevent dementia, research, including this study, suggests that addressing risk factors for poor cardiovascular health may also help reduce the risk of cognitive decline and dementia.”
Dr Richard Oakley, associate director of research and innovation at Alzheimer’s Society, added: “This study adds to growing evidence that looking after our heart health in midlife may help us live more years free from dementia.
“While no single action can guarantee that you won’t get dementia, evidence shows that what’s good for the heart is often good for the brain. Not smoking, keeping active and managing conditions such as high blood pressure and diabetes are all important steps people can take to support their long-term brain health.”
