Alzheimer's is the most common cause of dementia, afflicting more than 700,000 Britons.

To reduce the risk, research suggests that maintaining regular social interaction can contribute to maintaining brain health as we age – and possibly decrease the chance of developing the disease.

“Some evidence suggests remaining socially active may reduce your risk of dementia and living with someone is certainly a good way of increasing social interaction,” Dr Susanne Sorensen from the Alzheimer’s Society says.

“However, there are many other lifestyle factors associated with being married that may help reduce your risk of dementia, whether it's reaching for the vacuum cleaner or going for long romantic walks.”

The Society also says singletons shouldn’t worry as there are many other ways to reduce your risk of dementia that don't involve popping the question and running up the aisle.

“The best evidence is around eating a Mediterranean diet, exercising regularly and not smoking,” Sorensen says.

According to a recent report in the medical journal Neurology, eating fish three times a week may lead to a reduction in harmful brain lesions that can trigger Alzheimer's disease and stroke by up to 25 per cent.

According to the British Heart Foundation, 20 per cent of people in the UK who have dementia have vascular dementia. Keeping the risks low for that will also reduce your risk of developing other diseases of the heart and circulation.

The BHF have the following tips:

  • Stop smoking, or at least cut back.
  • Eat a diet low in saturated fat – cut back on hard cheese, fatty meat, biscuits, cakes and high-fat dairy products.
  • Keep to a healthy weight - healthy BMI below 25.
  • Be physically active - that means 30 minutes of activity (brisk walking, etc) five times a week.
  • Make sure your you have a test for diabetes if you have problems with frequent urination or thirst, if you have a family history of the illness, have a South Asian background or an apple-shaped body.
  • Have a cholesterol test if you have a history of high cholesterol in your family. Eat at least five portions of fruit and veg a day to improve good cholesterol.