Press Release

Low Jaw Strength reflects Hard to Swallow in Old Age

Published: February 18, 2022
Researchers led by Tokyo Medical and Dental University (TMDU) confirmed that jaw strength can be used as an index for swallowing difficulties in older adults

Tokyo, Japan – As we merrily eat and drink our way through life, we don’t put much thought into how often we work our jaw muscles. But, like all muscles, even the functioning of our jaw muscles declines with aging, putting us at risk for swallowing difficulties. Now, a research team led by Tokyo Medical and Dental University (TMDU) has found that older adults with higher jaw strength are less likely to have difficulties swallowing.

When a person is eating, their tongue consolidates food and pushes the food bolus toward the back of the mouth, while also exerting pressure on the airway to prevent the entry of food. Swallowing is a reflex; without conscious thought, muscles that extend from the tongue down to the horseshoe-shaped hyoid, lift the bone and open the esophagus to allow food to pass through. When a person has difficulty swallowing, which sometimes happens later in life, residue that is left behind can enter the airways and lead to serious complications like pneumonia.

One reason for difficulty swallowing is that the muscles that lift the hyoid bone can lose strength. Difficulty swallowing is also known as dysphagia, and until now, objective assessment of dysphagia has required carrying out an invasive procedure in a facility with specialized technology. However, in a study published in January in Gerontology, researchers have found that a jaw-opening sthenometer, which measures jaw-opening force, can be used to easily assess the risk of dysphagia. “Some of the muscles used to lower the jaw bone to open the mouth are also used in swallowing,” say corresponding author Koji Hara and  lead author Ryosuke Yanagida.

To use jaw-opening strength as an indicator of dysphagia, it was important to determine whether other factors affected the relationship between jaw strength and the presence of dysphagia. “In our comprehensive analyses, we considered the effects of multiple variables, such as age, sex, physical measurements like calf circumference, handgrip strength, and tongue pressure, the presence of other disorders, the ability to perform daily activities without the help of others, and at which facility the assessment took place,” explains senior author Haruka Tohara. “We found that jaw strength was a suitable variable for indicating the presence of dysphagia, after adjusting for age and sex.”

This study demonstrates that new findings can open avenues that lead to improvements in access to health care. There is now the potential to screen older adults for dysphagia as a matter of routine, because jaw strength can be easily assessed in many clinical settings.

How to measure jaw-opening force

・Patients are asked to relax and close their mouth.
・Place the adjustment belt and chin cap.
・The adjustment belt is secured as tightly as possible.
・Calibrate the value before each measurement.
・Patients are asked to open their jaws as wide as possible.

The article, “Jaw-opening force as a useful index for dysphagia: A cross-sectional and multi-institutional study,” was published in Gerontology at DOI:10.1159/000521392


A team of researchers led by Tokyo Medical and Dental University (TMDU) found that jaw-opening strength can be used to screen older adults for swallowing difficulties. These difficulties can arise later in life and lead to serious complications, but the use of a simple and non-invasive tool to measure jaw strength could enable easy identification of more older adults with swallowing difficulties before complications develop.

Journal Article


TITLE:Jaw-Opening Force as a Useful Index for Dysphagia: A Cross-Sectional and Multi-Institutional Study


Correspondence to

Haruka Tohara, Professor

Department of Dysphagia Rehabilitation,
Graduate School of Medical and Dental Sciences,
Tokyo Medical and Dental University(TMDU)

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