Researchers at the University of Missouri (MU), Columbia, Mo, have established a model that identifies aging as a key factor in the development of dysphagia, rather than a symptom of undiagnosed ALS or Parkinson’s disease. The new findings may help point to therapeutic treatments for the swallowing disorder, said to affect nearly 40% of Americans age 60 years and older.
“As people age, and especially once they’re 50 and older, their ability to swallow quickly and safely deteriorates with each advancing decade,” says Teresa Lever, PhD, assistant professor of otolaryngology at the MU School of Medicine and lead author of the study. “For years, we haven’t known why. Through our research with mice, we now know this disorder can occur naturally and independent of another disease. Our next step is to study this model to determine why age-related dysphagia, also called presbyphagia, occurs and identify ways to prevent it.”
A media release from MU notes that individuals affected by presbyphagia generally experience slow, delayed and uncoordinated swallowing that compromises airway function. This puts older individuals at risk for developing life-threatening malnutrition and aspiration pneumonia, which is caused when food or saliva is breathed into the lungs or airways. These risks are said to increase when an individual has an existing health condition, such as a neurodegenerative disease, head and neck cancer, or a major surgery.
Videofluoroscopy has long been the gold standard for diagnosing swallowing disorders in humans, according to the MU media release. Lever explains the university has a miniaturized fluoroscope and swallow test protocol that are unique to the school’s lab, and can determine whether a mouse has dysphagia.
“By studying the swallowing function of healthy mice over their lifespan, we found they exhibit many of the same symptoms of dysphagia as healthy aging adults,” Lever says.
The researchers established 15 metrics that could be compared to human swallowing function. These metrics include functions such as swallow rate, pharyngeal transit time — the time it takes liquid to be swallowed through the pharynx , or throat, and into the esophagus, or food tube — and the number of ineffective swallows through the esophagus. The researchers found that healthy aging mice develop symptoms of swallowing impairment that closely resemble the impairments seen in older adults: generally slowed swallowing function, impaired tongue function, larger size of the amount swallowed and an increase in the time it takes liquid to travel through the throat to the stomach.
“For years, we’ve only been able to treat the symptoms and have been unable to address the root causes of dysphagia,” Lever says. “Though more research is needed, this knowledge sets the stage for us to study ways to prevent, delay or potentially reverse swallowing disorders using new therapies.”
[Source: University of Missouri]