Curious Kids: why do older adults get shorter?

Hi I’m Miranda. I am ten years old and I live in California. My question is: why do older adults get shorter?

What an interesting question, Miranda!

Luckily, you don’t have to worry about this for some time. Until you are 30 or so (I know, it sounds old), you will continue to grow. However, after that, most people start to gradually shrink. So by the time you are 80 (yes, that seems really ancient), you would be 2-2.5 inches (5-6 centimetres) shorter.

Backs, muscles, joints

So, what exactly in your body shrinks this much? Ahh, this is another interesting question. The secret is in what keeps your body upright — your back. It is made up of 33 tiny little bones called vertebrae. Between most of these vertebrae are discs made of softer tissue.

The middle of these soft discs are like jelly, and are made mostly of water. These act like a shock absorber when you walk, run and jump.

As you get older, these discs slowly lose water and become a tiny bit flatter. But because there are usually 23 of these discs, they make up a quarter of the height of your back. When each of them shrinks a little bit, it all adds up and you get shorter.

Older people’s muscles also get smaller and weaker, their bones get thinner and the spaces between the bones in their joints get smaller. Together, this can also change your height.

People can shrink too much

While a small change in height in older people is normal, shrinking too much — more than 2 inches (5cm) — can be a bit of a problem. It may be a sign of a disease where your bones become too weak and brittle, and are easier to break.

As muscles get weaker, especially muscles that support your back, your back may get a curved “hunchback”, which makes you look even shorter. Weaker muscles can also cause a sore back and problems with balance.

So, is there anything you can do to stop getting shorter when you age? There certainly is. If you eat healthy food, exercise regularly and get outdoors to play in the sunshine from time to time, it will help keep your bones and muscles healthy and stop you getting too short when you are older.

Your height changes over the day

Another thing you may not realise is that even when you are young, your height changes throughout the day. You are actually tallest when you wake up in the morning, but you lose up to an inch (2.5cm) of your height within three hours of getting out of bed.

This is because when you sleep, your body rests and allows the water to get back into the jelly centres of the discs in your spine. But when you bounce out of bed, the pressure on these discs makes them lose water again and you get a little smaller.

So, if you really want to be the tallest you can be (getting picked for a basketball team, perhaps?), try to measure your height just after you get out of bed in the morning.

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