Why do adults get shorter as they age? And how much height do they actually lose?

When you picture an older person, you may imagine someone shorter and slightly stooped. It’s not just your imagination: most of us gradually lose some height as we age.

But how does it happen, when and by how much?

Here’s what the science says, and when it can signal an underlying health problem.

Our spine changes structure

Most lasting height loss happens in the spine. Think of the spine as a tower of bony blocks separated by water-filled cushions. The blocks are the vertebrae, and the cushions are intervertebral discs.

Over time, these discs lose water, change their structure and become less effective at maintaining the space between each vertebra.

A change in a few millimetres for each disc may sound trivial, but across the 23 intervertebral discs these small changes add up to a noticeable loss of height.

The gap between adjacent vertebrae is called the joint space. In some instances, a loss of this space can manifest as back pain or difficulty bending in certain ways.

It’s not just a reduction in joint space, though. The alignment of the spine can also change over a lifespan. We naturally have an S-shaped curve to our spines. When that curve becomes exaggerated through age-related spinal changes, the head and shoulders move forwards, causing us to measure shorter.

One factor that can contribute to this is muscle and ligament strength. Ligaments are tough bands of connective tissue that join bones. These can lose tension and strength with age, contributing to changes in posture and spinal height.

We also rely on our back and spinal muscles to help maintain joint height and mobility.

We naturally lose muscle strength and size as we age, which can lead to the spine progressively becoming more compressed and to changes in posture.

When does shrinkage start?

Some people notice small changes in their 30s, but height loss tends to become more noticeable from our 40s and accelerates later in life.

In one long-running study, men lost an average of about 2cm between age 36 and 69, while women lost about 2.4cm.

Bone loss contributes in a different way. As we age, the balance between bone formation and bone breakdown shifts. Much of our body relies on calcium for normal function, and our bones act as our natural calcium store. Throughout life we are constantly balancing bone rebuilding against bone loss.

From around age 30 to 40, we begin to lose bone slightly faster than we replace it, potentially leading to osteoporosis. Osteoporosis alone does not necessarily make bones shorter; it makes them less dense and more fragile. A weakened vertebra may compress or become wedge-shaped, reducing spinal height and potentially leading to a stooped posture.

Menopause also accelerates bone loss, which probably helps explain why women lose slightly more height on average.

What does height loss tell you?

Putting this all together, height loss can be viewed as a marker of underlying bone, muscle and ligament health.

For instance, Australian osteoporosis guidance says a height loss of 3cm or more should prompt an X-ray to rule out a deformed or fractured vertebra. A Canadian study found that people who had lost at least 3cm in height had more than double the risk of a later fracture.

Studies have also suggested that people with greater height loss are more likely to be frail, have lower muscle strength and density, and experience poorer health outcomes overall.

Sometimes these broader health changes affect bone health, rather than the bone-related changes themselves being the cause of declining health.

Height loss is one of the few visible changes of ageing that can tell us something meaningful about what is happening inside the body. While a gradual decrease in height is usually a normal consequence of changes in the spine, more substantial losses can be a sign of osteoporosis, vertebral fractures or declining muscle health.

Can you stop it?

Not entirely. Exercise cannot restore a damaged vertebrae or reverse a compressed joint space.

But strength, balance and posture matter. Research shows targeted exercise can slow the rate of vertebral height loss or, in some cases, help restore standing height by correcting age-related spinal curvatures.

What’s normal and what’s not?

Becoming a little shorter is a normal part of ageing. Becoming much shorter may be your spine’s way of asking for attention. That’s why it’s worth keeping track of your height throughout adulthood.

Measure your height regularly (a number remembered from a teenage driver’s licence is not a reliable baseline). Measure without shoes, using the same equipment where possible, and at roughly the same time of day.

Talk to your doctor if you lose 3cm or more, or the change is accompanied by new back pain, a more pronounced stoop or other changes in posture.