More than 30 million people worldwide live with Alzheimer's disease, and while researchers are pushing hard to find a cure, their efforts so far have met with failure. With no effective treatment on the horizon, prevention has become the only game in town. But what can be done to reduce the risk of dementia?
In research published on Thursday, US scientists claim that a form of computer-based brain training can reduce the risk of dementia by 29%. The training was designed to speed up people's visual information processing, for example by having them spot a on a screen, and a truck on the periphery of their vision, at the same time. Those who are claimed to have benefited trained for an hour, twice a week, for five weeks, and some went on to have booster sessions at the end of the first and third years. To see if the training made any difference, the participants set tests up to 10 years later.
There are good reasons to be cautious about the results, which appear in the journal Alzheimer's and Dementia: Translational Research and Clinical Interventions. The study wasn't designed to examine dementia, and the scientists didn't rely on a clinical diagnosis when they totted up who had the dementia at the end of the trial. Instead, they opted for a broader definition and allowed people to self-report that they had the disorder. "If you're going to say you are preventing dementia, you want that defined to the nth degree," said Peter Passmore, an Alzheimer's researcher at Queen's University in Belfast.
The scientists actually tested two other kinds of brain training too. These were designed to strengthen memory and mental reasoning respectively. A decade after training began, the scientists found that 22.7% of people in the speed training group had dementia, compared with 24.2% in both memory and reasoning groups. In a control group of people who had no training, the dementia rate was 28.8%.
But in studies like these, scientists have to take into account whether an intervention might look good or bad simply by chance. The results for the memory and mental reasoning brain training failed this statistical test. More importantly, the effect linked to visual processing was at best at the very edge of statistical significance. Scientific convention has it that if the chance of a result being a fluke is greater than 5%, it is not worth taking seriously. For visual speed training, the figure was 4.9%.
"We're lacking high quality evidence to show that brain training has any impact on the risk of dementia, and based on current studies we can't recommend people take it up," said Clare Walton, research manager at the Alzheimer's Society. "What we do know is that keeping the body and brain active across life can go someway towards reducing the risk."
There are some risk factors for dementia that we cannot change, such as age, genetic makeup, gender and ethnicity. And it may be too late to do much about others. Spending more years in education as a child, for example, has a protective effect against dementia, but whether returning to education later in life helps is unclear.
Until effective treatments are found, the most promising way to reduce dementia risk is through lifestyle changes. Smokers are estimated to be 30-70% more likely than nonsmokers to develop dementia, so quitting immediately is a good start. High blood pressure in midlife seems to raise the risk too, and better control of blood pressure may be one reason the rate of new cases of dementia in Britain has dropped in recent years.
Alzheimer's researchers often say that what's good for the heart is good for the brain. The basis for the claim comes largely from research on exercise and diet. It shows that regular aerobic exercise can reduce dementia risk by 30-40%, while eating a healthy Mediterranean-style diet rich in fruit, vegetables and oily fish, and low in red meat and sugar, can potentially halve the risk of dementia.
Walton advises people to take up a hobby that hits a number of risk factors all at once. Joining dance classes or a table tennis club is a way to get exercise, to challenge the brain by learning new skills and to socialize, for example. "The best thing is to find activities that do all three," she said.
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