Can your jaw structure predict if you'll shrink as you age? - study

Structural changes to a woman’s jawline might help predict if she will experience age-related height loss, according to a new study published this month.

The peer-reviewed article, published in the academic journal BMJ, suggested that dentists should use their privileged information on patients' jaws to speak to patients about preventing shrinkage.

Women tend to experience more rapid height reduction after they turn 75 years old, according to the study. This is problematic because shrinkage is associated with an increased risk of ill health and death.

Why do people experience height loss?

There is no consensus in the scientific community for what causes height loss. However, it has been suggested that progressive skeletal deformation, fallen arches in the feet and altered posture, or degenerative processes including osteoporosis, compressed or lost discs in the spine, and vertebral fractures may all play a role. 

How did the researchers come to their conclusion?

The researchers looked for a relationship between general bone health, cortical erosion, meaning loss of the outer layer of the bone, and trabecular sparseness in the jawbones of 933 female participants.

The women, who all originated from Sweden, have been under assessment since 1968. All the women were aged 38, 46 or 54 years old when they first joined the study.

Each participant underwent health checks, during the data collecting period, which included measurements of their height and weight and a dental check-up at least twice during the monitoring period. 

To calculate height loss, the researchers collected data on the participants’ heights over three periods of 12-13 years. 

The average height loss for the participants ranged from 0.075 cm, 0.08 cm, and 0.18 cm annually over the three observational periods. This amounted to up to 0.9 cm, 1 cm, and 2.4 cm in height loss total for all three periods. 

The percentage of participants with a severe amount of cortical erosion increased from over three percent in 1968–80 to over 11% in 1980–92 and a little below 50% in 1992–2005. 

Similarly, the percentage of sparse trabeculation increased from 20+% in 1968–80, to 33.5% in 1980–92, and to nearly 42% in 1992–2005.

Throughout the study, the researchers found that those with severe cortical erosion and those with sparse trabeculation experienced a greater height loss.

The study may require more work

As the study is observational, it's not fully reliable to establish a cause-and-effect relationship. Correlation does not necessarily mean that there is causation. 

Additionally, not every participant that began the study completed it. This meant a smaller sample size and there is a risk that the data could be skewed. 

The structural bone changes seen in the jawbones of the participants likely may be those of the vertebrae. This would explain the potential height loss. 

“Since most individuals visit their dentist at least every 2 years and radiographs are taken, a collaboration between dentists and physicians may open opportunities for predicting future risk of height loss,” the researchers explained.