Other studies have found improvements in cognitive function after a combined regimen of physical exercise and cognitive training.

But skeptics say there is no guarantee that intellectual stimulation will prevent Alzheimer’s disease or other forms of dementia. “Maybe it does, but I don’t think we have a shred of evidence,” said Dr Robert N Butler, a psychiatrist and gerontologist who is president of the International Longevity Center-USA. “What it does is maintain good health,” he said, adding, “I don’t think we can go much further than that.”

But there is consensus among scientists on a few recommendations for action that, most agree, cannot hurt.

Regular physical activity may improve brain function, both by increasing blood flow to the brain and stimulating the production of hormones and nerve growth factors involved in neurogenesis. Animal studies have found that physically active animals have better memories and more cells in their hippocampus. Exercise also plays a role in countering diseases like Type 2 diabetes, which increases the risk of dementia. Cholesterol and hypertension, which affect vascular health, also need to be kept in check.

Seeking out stimulation through interesting work, volunteer opportunities or continuing education is beneficial.

Travel, read, take up a new language or learn to play a musical instrument. Staying socially connected is also associated with brain health, as is managing stress effectively. Chronic stress can lead to the rewiring of areas of the brain that are involved in emotion, memory and decision-making, Dr McEwen said, “and the brain becomes more biased toward more anxiety, more depression, less flexibility in terms of decision-making and becomes less able to store information.”

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