We all know that smoking and drinking aren't good for your health, but new research has linked them to an increased risk of dementia.

It's claimed that both vices can impact the amount of grey matter in your brain, which is what helps you deal with information and retain memories.

The study involved 1,600 people, who each filled out questions designed to give maximum information about any unhealthy lifestyle habits they had. Seven years later, the group, half of which were under 50, had their brains scanned and sat for IQ tests. This was to find out if any of them were already showing signs of dementia of any kind, with three parts of the brain looked at in depth. They were the hippocampus, precuneus and posterior cingulate cortex, which are all important when it comes to memory and information retention.

It was discovered that alcohol and being obese had links to a smaller brain in general, while smoking and being obese led to a reduced posterior cingulate cortex.

Combining smoking and drinking affected the size of the hippocampus, while people who had high blood pressure, were obese and drank saw a reduction in their precuneus.

The IQ tests showed that a lower volume in any of these three brain areas meant people couldn't remember information as well.

"We currently do not have effective treatments for Alzheimer’s disease, so the focus is on prevention," Dr Kevin King, of the University of Southern California in Los Angeles, said in the findings published in the journal Radiology.

"In the future, we may be able to provide patients with useful and actionable information about the impact different risk factors may be having on their brain health during routine clinical imaging."

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