Here’s what you can do at any age, from Australia's trusted, straight-talking doctor and broadcaster Dr Norman Swan.

Your 20s

• Don’t smoke burnt plants of any kind or vape crap that was never meant to be burnt. Try not to use alcohol or other drugs to the extent that they change your mental state. Getting drunk or high are signs of binge use, which is not good for your brain health.

• Get as much formal education as you can. It reduces your chances of dementia when you’re older or, at the least, delays it and can possibly counteract the effect of genes you might have inherited which increase the risk of dementia.

• At least once in your 20s, get your GP to check your blood pressure and cholesterol in case you need to change your eating, alcohol intake and exercise levels.

• Start the habit of eating a plant-based diet with not too much red meat. Now’s the time to get into the habit of mild calorie restriction in association with moderately intense exercise. The easy way might be intermittent frugality every three days or so (see Intermittent Frugality). Also a plant-based diet is in itself low in calories relative to the nutrition you get and satisfying.

• Exercise for 45 minutes to an hour most days of the week, reasonably intensively, and include muscle strengthening in each session. Now’s the time to get into the habit of developing and maintaining strong muscles.

• Watch your weight (see calorie restriction above).

• Avoid food fads and be careful about time-restricted eating which, along with screen time, may screw up your body clocks and start an accelerated ageing process.

• Severely limit screen use after dark, make sure your bedroom doesn’t let in street lighting and don’t mess with mealtimes. In other words, get your circadian rhythm into shape. It’s good for both mental and physical health.

• Seek help for depression and anxiety if you’re experiencing them. Depression, in particular, may contribute to accelerated ageing.

• In your 20s, your elderly relatives are likely to still be alive. Now’s the time to find out who in your family died of what and at what age, so you can get an idea of any genetic risk you could have inherited. Seek genetic counselling if something does turn up.

• Don’t assume that because you’re young, you’re not at risk of anything. Any lumps, bleeding, bruising, unexplained weight loss or pain, see your GP.

• Start cervical cancer screening when you’re 25, assuming you’ve been sexually active.

• Get yourself a good GP whom you trust and like.