Three million cases of Alzheimer’s across the world could be prevented in seven easy ways, a study in The Lancet Neurology suggests.

A mixture of keeping healthy, and exercising could help many dodge the “epidemic” of Alzheimer’s, according to a review by psychiatrists published today.

Quitting smoking, increasing physical activity, enhancing mental activity, controlling you blood pressure and diabetes risk factors, as well as managing depression and obesity can all help combat the disease.

The study shows lifestyle and dietary risk factors might cause as many of 50% of cases of Alzheimer’s disease worldwide.

Lead author Dr Deborah Barnes of the University of California told the Huffington Post UK: “I think it’s exciting that our study suggests half of cases of Alzheimer’s may be due to risk factors that are modifiable. If we can change our behaviour a bit it could help with this epidemic.”

Dr Barnes added: “The policy implications are worldwide. They’re huge.”

Professor of Psychiatry of older people at University College London University Gill Livingston said the study showed it was time to start looking at “brain health” as well as “heart health”.

Professor Livingston said there was a genetic component to the disease, but being “active” may to help stave off the illness. She said other studies had shown that being socially as well as mentally and physically active was also helpful.

“ Its an exciting time with lots of advances. We are also going to need an array of drugs and strategies to help prevent the illness occurring and progressing and help families as well as people with the illness cope with it .”

The news comes as separate study UK in the Lancet concludes that two main antidepressants prescribed to dementia sufferers do not work.

The study suggests sertraline or mirtazapine can have side effects on those with dementia and work no better than placebos.