Regular exercise, a healthy diet, brain training and social activities were found to help stave off mental decline.
The study is the first large-scale human trial to show that healthy living can help maintain or even improve brain function.
It found those at risk of dementia put on a two-year lifestyle programme performed 25 percent better in brain tests than those who received only basic health advice.
The University of Eastern Finland, the National Institute for Health and Welfare in Helsinki, and Sweden’s Karolinska Institutet in Stockholm, assessed almost 1,300 people aged 60-77.
Lead researcher Professor Miia Kivipelto said the study showed an ‘intensive programme’ addressing diet, heart health and fitness might ‘prevent cognitive decline in elderly people at risk’.
Previous studies have estimated preventive action could cut one in five new cases over the next 20 years. The latest research split participants into two groups – one receiving simple health advice, and the other in-depth guidance on nutrition, exercise, cognitive training and social activities.
The diet included high amounts of fruit and vegetables, wholegrains, low-fat dairy and meat, less than 50g sugar a day and fish at least twice a week. The scheme recommended muscle training between one and three times a week and aerobic exercise two to five times a week.
Brain training included sessions with psychologists and regular computer-based exercises at home. The intervention patients also had regular heart check-ups with a nurse or doctor. After two years, the intensive group’s overall scores in brain tests were 25 percent higher than the other group.
In some areas, the difference was even more striking. On the brain’s ability to organise thoughts, results were 83 percent higher among those on the lifestyle programme, and they were 150 percent better at processing.
Dr Simon Ridley, of Alzheimer’s Research UK, said the ‘promising’ results suggest ‘improving cardiovascular health and keeping mentally active could slow decline in some aspects of our thinking’.
But Alzheimer’s Society’s Dr Doug Brown said more research is needed into how to ‘protect the brain in the longer term’.
The participants will be re-tested in seven years to determine whether intervention cuts dementia.