It may be possible to ward off or prevent one of the most common types of dementia, a new long-term study suggests.

The risk of cognitive decline increases as we get older, with about 42% of Americans over the age of 55 expected to develop dementia during their lives.

The research, published Wednesday in the journal Neurology Open Access, found that people who avoid three vascular risk factors in middle age — high blood pressure, diabetes and smoking — had about 13 more dementia-free years.

For the study, NYU Langone Health researchers tracked about 12,400 middle-aged participants in the U.S. for about 26 years. At the start, their average age was 56. Just over half of participants were women and about 25% were Black. None of the participants had signs of vascular cognitive impairment, a condition linked to strokes and small-vessel disease.

The researchers compared people who were diagnosed with the risk factors of diabetes, hypertension (blood pressure of 140/90 mm Hg or higher) and who used tobacco to those with none. Diabetes, hypertension and smoking cause damage to blood vessels, including those that supply the brain.

For people with the three risk factors, dementia risk rose from 23% at age 55 to 37% at 75. By 85, only 7% of people with all three risk factors were dementia-free.

People with the three risk factors had an about 18 dementia-free years of their lives, compared to an estimated 30 years for those with no risk factors.

Dr. Josef Coresh, the director of the Optimal Aging Institute at NYU Langone Health and an author of the study, said the researchers wanted to summarize the effects of midlife health habits on dementia and to give a simplified, “bottom-line” message for the population.

“We found if you had more risk factors, you had an elevated risk of both dementia and mortality,” Coresh said.

The findings reinforce evidence that healthy blood vessels not only protect against heart disease, but also protect brain health, said Dr. Cynthia Carlsson, a geriatrician at University of Wisconsin Health, who was not involved in the study.

Dr. Anna S. Nordvig, neurologist at Weill Cornell Medicine and NewYork-Presbyterian, said that if brain tissue is no longer receiving proper nutrition and blood flow, then that can lead to cognitive decline.

“Those three risk factors are all known to contribute to both small and large blood vessel disease in the brain,” said Nordvig, who was not involved in this study. “Controlling anything that improves cardiovascular health will also improve brain health.”

Prevention is crucial since there’s no cure for vascular dementia or Alzheimer’s, Coresh said. The NYU research focused on vascular health, although many of the same risk factors also contribute to Alzheimer’s, Coresh said. “Vascular health in midlife influences Alzheimer’s pathology,” he later said via email. “Treating vascular risk works on both fronts.”

About half of dementia is preventable through lifestyle changes, Coresh said. “There’s a lot you can do.”

Experts agree that it is never too late to start addressing vascular health.

“I encourage people to start with something tangible,” Carlsson said. “It’ll be different for each person based on what their risk profile looks like.”

Nordvig said that in addition to the three factors included in the research, she recommends focusing on other critical risk factors for dementia, such as high cholesterol, sleep apnea and obesity.

“Fifty-five [years old] is a great time to drastically improve your future of vascular health, both in your body and in your brain, and that also means slowing down dementia,” Nordvig said.