2. Follow a Mediterranean diet
One in three Britons over the age of 65 will develop dementia, with the risk increasing as you get older (your chance of developing Alzheimer's disease, the most common type of dementia, doubles every five years after 65).
See also: Five medical issues that can be mistaken for dementia
See also: Eight hidden signs of dementia
While there are some risk factors you can't do anything about, like your age and genetics, lifestyle factors play a large part too. Here are 10 things you can do today to lower your risk.
1. Exercise regularly
Keeping physically active is one of the best ways to reduce your risk of dementia. Regular aerobic exercise - the kind that makes your lungs work and gets your heart pumping - is the most effective as it encourages oxygen-filled blood to flow to the brain.
Scientists in America found that even 65-year-olds with the gene APOE-e4 (which increases the risk of Alzheimer's) were protected by brisk walking, jogging, swimming or cycling.
The Alzheimer's Society suggests doing moderately intense exercise that raises your heart rate for at least 30 minutes, five times a week.
Eating a healthy, balanced diet has been proven to reduce your risk of developing dementia, as well as lower your risk of many other illnesses, including cancer, diabetes and heart disease.
Experts recommend eating a Mediterranean diet with plenty of fresh fruit and vegetables, oily fish, nuts, seeds and olive oil. At the same time, eat only small amounts of dairy products, meat, saturated fat, sugar and processed foods.
While there is no one 'magic' superfood, research shows that people who eat a diet high in omega-3 fatty acids, in foods like oily fish and walnuts, are less likely to develop dementia.
Oily fish also contains vitamin D – low levels of which have been linked to mental decline in old age. Aim to get 20-30 minutes of sunshine three times a week, eat foods like oily fish, eggs, fortified cereals and milk, or consider taking a vitamin D supplement.
3. Keep your weight in check
There's another good reason to exercise regularly and eat a healthy diet. Keeping your weight in check will reduce your risk of developing high blood pressure and heart disease, both of which put you at greater risk of developing dementia.
4. Get your blood pressure checked
Conditions which affect the heart, arteries or blood circulation (such as diabetes, heart problems and stroke), significantly increase the risk of developing dementia. Studies show that one-in-three people who have a stroke will go on to develop dementia.
Keeping your blood pressure and cholesterol levels in check is important once you get over the age of 40, particularly if you have a family history of dementia or cardiovascular disease. See your GP for a regular check-up or invest in a blood pressure monitor and check your levels at home.
5. Cut back on saturated fat and salt
To keep your heart and circulation healthy, as well as your brain, cut back on saturated fat. Too much can cause narrowing of the arteries, making heart attack or stroke more likely. The NHS recommends that the average man eat no more than 30g of saturated fat a day and women no more than 20g.
As well as cutting back on obvious foods – such as butter, pies, cakes, biscuits, sausages, bacon, cheese and cream – keep an eye on nutrition labels to see how much you're eating. Most have a green-light system to show when a particularly food is high in saturated fat.
Watch your salt intake too, as too much can increase your risk of high blood pressure. Adults should eat no more than 6g of salt a day – again check food labels, especially on things like tinned and fresh soup and processed meals which can be surprisingly high in salt.
6. Quit smoking
Smoking significantly increases your chance of developing dementia, and has a damaging effect on the heart, lungs and vascular system, including the blood vessels in the brain.
Quit and you'll lower your risk of developing cardiovascular diseases and cancer, as well as dementia.
Your GP can offer nicotine replacement products and medication to help you quit, and refer you to your local NHS Stop Smoking support service. Or call the NHS Stop Smoking helpline on 0800 022 4332.
7. Drink alcohol in moderation
Too much alcohol significantly increases the risk of developing dementias – but some research suggests that light-to-moderate amounts of alcohol may protect the brain against dementia and keep the heart and vascular system healthy.
The NHS recommends sticking to a daily limit of three to four units for men, and two to three units for women – with preferably two alcohol-free days a week. A unit of alcohol is equal to about half a pint of normal-strength lager, a small glass of wine or a pub measure (25ml) of spirits. One small glass of red wine per day as part of a Mediterranean diet is fine.
8. Keep in contact with friends
Loneliness in old age has been shown to have a negative effect on our general health and wellbeing - and studies show that older people who are more socially active have a slightly reduced risk of developing dementia.
Keeping in touch with friends and relatives, as well as going along to clubs, places of religious worship and volunteering can all be of benefit.
9. Give your brain a workout
Finally, your brain needs a workout, not just your body. Evidence suggests that older people who keep their brains active by reading, learning and doing puzzles, are less likely to develop dementia.
If you'd rather paint, draw, sculpt or write poetry than do Sudoku puzzles, there's good news. According to a study published in the medical journal of the American Academy of Neurology, people who engaged in creative pursuits in old age were 73 percent less likely to develop dementia.