A study led by an assistant professor at the Medical University of South Carolina broke new ground by looking at the frequency and progression of hearing loss over a 25-year period.
“No studies had looked at this over such a long follow-up time,” said Lauren Dillard, Ph.D., AuD. She’s with the Department of Otolaryngology-Head and Neck Surgery at MUSC.
“When we looked at the existing research, there were only four unique cohort studies that reported the number of new cases of hearing loss over time. That was shocking because hearing loss is such a common issue, and in order to do anything about it, we need this sort of basic, fundamental information to know what it looks like in the population.”
Her team, which included colleagues at MUSC, Boston University, Harvard Medical School and the University of Texas-San Antonio, was able to gather that fundamental information, thanks to what’s been called “the crown jewel of epidemiology”: the Framingham Heart Study.
That study, which the U.S. Public Health Service launched in 1948 in Framingham, Massachusetts, was designed to find factors that play a role in heart disease. It is still active today and includes more than 15,000 people from three generations of participants.
“Over the years, they’ve incorporated hearing measures into the study as well,” Dillard said.
Through collaborations with researchers from the Framingham Heart Study, Dillard’s group was able to analyze hearing loss data collected from about 500 people in the study who were part of a group called the Offspring Cohort (the children of the original participants). Dillard’s team published the results in JAMA Network Open.
“First, we saw that a lot of people are developing hearing loss as they age. Over half of this sample that we looked at developed hearing loss over 25 years of follow-up time.” Dillard said.
That sample included people with an average age of 52 when they started. The fact that so many of them ended up with hearing loss may say something about what’s happening to older adults more broadly.
“Hearing loss can be very impactful. It can restrict communication, and it's not just it's a physical ailment. It impacts the way that we interact with the people around us and the people that we love.”
Knowing that, her team also looked at some other potential factors related to hearing loss with the hope of finding ways to prevent it.
Key findings include:
-People with lower education levels ran a higher risk of hearing loss. “Is that because if you have less education then you’re more likely to have other experiences that could lead to hearing loss?” Dillard said. “That’s hard to tease out.” Previous research has linked lower education levels to other health problems.
-Noise exposure caused hearing loss but did not cause it to progress afterward. Previous studies produced conflicting results, so the new research may provide a clearer answer. Key sources of noise exposure include things like target shooting and noise exposure at work.
-Hypertension (high blood pressure) and stroke risk raised the risk of hearing loss. “We live in one body, and everything is connected,” Dillard said. “The hearing organ, which is the cochlea, located in the inner ear, is a very vascular system. It's fed by blood supply like the rest of our body. And so, like many other health-related conditions, it's affected when that blood supply is restricted.”
Dillard’s team also looked at the severity of hearing loss. Among participants who started the study with no hearing loss, it found:
-66.9% developed mild hearing loss.
-27.3% had moderate hearing loss.
-5.7% had hearing loss that was moderately severe or worse.
The rates were similar for men and women.
Dillard hopes the study raises awareness about hearing loss. “This could serve as motivation for us to think about our hearing earlier in life and to take the correct measures to protect ourselves.”
Research has found that untreated hearing loss has social and emotional effects, including isolation, depression, anxiety and paranoia. “It's not just it's a physical ailment. It impacts the way that we interact with the people around us and the people that we love,” Dillard said.
