Everyone's guilty of forgetting someone's name, where you last put your car keys or why you phoned your friend. Young people tend to laugh off these ‘senior moments', but for those who are 50-plus and on the lookout for any signs of the big ‘D' - dementia - it can be spooky.

Physical activity at any age can greatly improve brain health, but to stay sharp in your later years, brain exercises are important too.

‘Our research has shown us what's good for the heart is good for the brain and vice versa,' professor of psychogeriatrics Henry Brodaty says. ‘It's clear good lifestyle habits through our 20s, 30s and 40s, such as a healthy diet, no smoking and plenty of exercise combined with active mind games and plenty of sleep, will affect our brain in our 70s and 80s.'

Any exercise that gets us huffing and puffing is best for increasing blood circulation to the brain. This relieves the build-up of toxic debris that comes with ageing.

‘Use your brain actively,' Professor Brodaty advises. ‘Don't let television wash over you, and don't worry about over-straining your brain. It's not like physical exercise where you can do too much. Read a book or watch a movie, then tell someone about it.'

If you want to enjoy a healthy ‘golden age', here are a few ways to put a new spin on old habits and exercise your brain at the same time:

Use your non-dominant hand for familiar chores such as brushing your teeth.

Vary your walking, running or cycling route.

Swap your favourite board game or television show for something new.

Rearrange the furniture in your house.

Try out an exciting or exotic new recipe.

Read an article about an unfamiliar topic. Test your grey matter.

Doing brain exercises can improve an elderly person's memory and mental agility by 10 years. Work on your brain fitness by attempting to answer these mind stimulators. You'll find the answers at the bottom of the page.

1. Find the letter ‘F'

Count the number of times the letter ‘f' appears in the following sentence:

‘Finished files are the result of years of scientific study combined with the experience of years.'

2. Making cents

Without looking, describe the pictures on the tail sides of the 10 cent piece and $2 coin.

Even though we can survive without knowing the answer, this example shows that our attention and memory are selective.

3. Guess-timations

Regardless of whether your answer is correct or not, putting your brain to work is worthwhile. Guess-timate the answers to the following:

a) How heavy is a large commercial aeroplane such as a Boeing 747?

b) How many pairs of shoes have you owned in your life?

c) What did you do on the Monday after Christmas last year?

Answers - Test your grey matter

1 There are six occurrences of the letter ‘f' - but almost everyone guesses three. The brain has trouble processing the word ‘of' because the ‘f' sound is pronounced ‘v'.

2 A Maori carved head appears on the 10 cent piece, and a kotuku (white heron) on the $2 coin.

3 a) An empty Boeing 747 weighs around 182,000kg, and its maximum take-off weight is 375,000kg.

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