Wild new study links body part size to dementia risk

You may be able to tell how well your brain will age based on the size of one small muscle, according to a new study.

Doctors at Johns Hopkins measured the temporalis, a thin muscle that runs from the side of your skull to the jaw joint, in more than 500 healthy adults.

They observed them for five years to check for signs of dementia and found that people with smaller temporalis muscles were 60 percent more likely to develop dementia.

As people age, they naturally lose some of their muscle volume, but people with dementia tend to lose muscle mass faster than people without the memory-robbing disease.

So researchers like the Johns Hopkins group have started investigating whether they can use muscle loss as a predictor of dementia.

Normally the disease is diagnosed after it has progressed to the point where doctors can do little to intervene.

Scientists are therefore looking for a cheap, easy way to diagnose someone before symptoms start. Then the hope is that maybe they can start fighting back. This can include incorporating things like resistance training, exercise and better nutrition.

Study author Dr Shadpour Demehri said: ‘These interventions may help prevent or slow muscle loss and subsequently reduce the risk of cognitive decline and dementia.’

While estimates vary, some models, such as the Alzheimer’s Association chart above, predict that the number of dementia cases will continue to grow through 2050. This is partly due to an aging population.

About 7 million Americans are currently living with dementia. Some predictions estimate that this number will exist almost doubled by 2040 – Reach 12 million people.

Cheap methods to diagnose the condition early so people can act quickly to potentially prevent some of the changes associated with dementia.

Researchers have known for some time that people with this condition begin to lose muscle mass quickly.

Separate studies had suggested that the temporalis muscle may be a good predictor of how muscles will behave throughout the body.

So the Johns Hopkins researchers looked at it for their study, which was presented at the Radiological Society of North America annual meeting, it has yet to be published in a journal.

They studied 621 people aged around 70 who were healthy when they started the study.

For an average of five years, they monitored the muscle structure of their participants by placing them in an MRI machine, which provides detailed images of bones, muscles and blood.

Based on the photos they took, they sorted people into two groups.

A total of 131 participants were in the large muscle group and 488 participants in the small muscle group.

They then looked at the development of dementia by monitoring the amount of tissue loss from the brain and giving them regular cognitive tests.

Doctors found that people with a smaller temporalis muscle were 60 percent more likely to develop dementia, even after adjusting for factors like age.

Study author Dr. Kamyar Moradi, who studies radiology at Johns Hopkins, said: ‘This is the first longitudinal study to show that skeletal muscle loss may contribute to the development of dementia.’

The temporalis muscle helps move the jaw and is especially useful in chewing. People can feel it in action by placing their hand on their temple and clenching the jaw

Dr. Max Wintermark, a neuroradiologist at the University of Texas who was not involved in the study, told MedPage today that more research is needed before it can be concluded that the temporalis muscle is a good predictor of dementia risk.

Dr. Wintermark said: ‘In this particular case it is difficult to know whether muscle loss is really a risk factor for dementia or is a result of the processes that lead to dementia.’

Still, he agreed with the study authors that working to maintain muscle mass and cardiovascular health in old age is likely helpful in preventing dementia.

However, working to maintain muscle mass makes sense, Wintermark agreed.

Although research has not shown that exercise or other interventions can stop this deadly disease, early studies have suggested that making lifestyle changes can reduce a person’s risk and symptoms of dementia.

In an article from 2024 from the University of Washington, researchers said early studies show that both cardio and resistance training can help make brain tissue more robust into old age.

This in turn could help slow the progression of dementia, buying back crucial years of normality.

Dr. Wintermark said, “In general, having a healthy lifestyle with adequate exercise is beneficial in many ways, including maintaining muscle mass.”