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.

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. A recent U.S. report was much more cautious, saying there are encouraging hints that lifestyle changes can bolster brain health but little if any proof.

Still, it’s never too early to try, said Lancet lead author Gill Livingston, a psychiatry professor.

“Although dementia is diagnosed in later life, the brain changes usually begin to develop years before,” she noted.

Next year, a $20 million U.S. study will test if some simple activities truly help older adults stay sharp. In the meantime, Alzheimer’s specialists say there’s little down side to commonsense recommendations.

A Lancet-appointed panel created a model 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.

The strongest evidence that lifestyle changes help comes from Finland, where a large, randomized study found older adults at high risk of dementia scored better on brain tests after two years of exercise, diet, cognitive stimulation and social activities.