WASHINGTON — There are no proven ways to stave off Alzheimer’s, but a new report raises the prospect that avoiding nine key risks starting in childhood just might delay or even prevent about a third of dementia cases around the world.

How? It has to do with lifestyle factors that may make the brain more vulnerable to problems with memory and thinking as we get older.

Thursday’s report in the British journal Lancet is provocative — its authors acknowledge their estimate is theoretical, based on statistical modeling.

“Although dementia is diagnosed in later life, the brain changes usually begin to develop years before,” said Lancet lead author Gill Livingston, a psychiatry professor at University College London.

Early next year, a $20 million U.S. study will begin rigorously testing if some simple day-to-day activities truly help older adults stay sharp. In the meantime, Alzheimer’s specialists say there’s little downside to certain common-sense recommendations.

“Increased health of the body supports increased health of the brain,” said cognitive neuroscientist Laura Baker of Wake Forest School of Medicine in North Carolina, who will lead the upcoming U.S. study.

Here’s the latest from last week’s Alzheimer’s Association International Conference on possible ways to guard your brain:

KEY RISKSA Lancet-appointed panel created a model of dementia risks throughout life that estimates about 35 percent of all cases of dementia are attributable to nine risk factors — risks that people potentially could change.Their resulting recommendations: Ensure good childhood education; avoid high blood pressure, obesity and smoking; manage diabetes, depression and age-related hearing loss; be physically active; stay socially engaged in old age.The theory: These factors together play a role in whether your brain is resilient enough to withstand years of silent damage that eventually leads to Alzheimer’s.

WHAT TO CHANGELast month, the U.S. National Academies of Sciences, Engineering and Medicine reported there’s little rigorous proof. That report found some evidence that controlling blood pressure, exercise and some forms of brain training — keeping intellectually stimulated — might work and couldn’t hurt. Why? What’s good for the heart is generally good for the brain. In fact, high blood pressure that can trigger heart attacks and strokes also increases risk for what’s called “vascular dementia.”And exercising your gray matter may bulk up the brain, whether it’s from childhood education or learning a new language as an adult. The more you learn, the more connections your brain forms, what scientists call cognitive reserve. Some U.S. studies have suggested that generations better educated than their grandparents have somewhat less risk of dementia.

LOOKING FOR PROOFThe Alzheimer’s Association is funding a study to find out if changes can help, in 2,500 cognitively healthy but high-risk older adults next year. They’ll test:- Walking — supervised, so no cheating. Wake Forest’s Baker puts seniors on treadmills at the local YMCA to avoid bumpy sidewalks. She starts exercise-newbies at 10 minutes a day for two days a week and works up to longer walks on more days.- A diet that includes more leafy greens, vegetables, whole grains, fish and poultry than the typical American menu.- Certain brain games and what Baker called an “intellectual stimulation barrage,” outings and other steps that keep people social.- Improving control of medical conditions like high blood pressure and diabetes that are toxic to the brain.