New study makes a staggering link between hearing loss and nutrition
A breakthrough study in Nepal demonstrates a definite link between early childhood undernutrition and adult hearing loss — with implications for the rest of the world.
It may come as a surprise, but hearing loss is estimated to affect more than 1 billion people worldwide. Even more shocking: the World Health Organization estimates that up to 60 percent of this global hearing loss is preventable.
A breakthrough research study published last week may start to better focus efforts on the problem. Researchers at Johns Hopkins and Duke Universities have shown that both acute and chronic forms of undernutrition during children’s preschool years are associated with hearing loss when those individuals become young adults. This study — the largest of its kind, with 16 years of follow-up in rural southern Nepal — could have a massive impact on hearing loss prevention in low-resource settings, where undernutrition is particularly common.
Here, Duke ear surgeon and TED Fellow Susan Emmett, the lead author on the paper, tells us about the breakthrough study and explains how it could affect how we think about — and prevent — hearing loss for millions of people.
What’s the link between nutrition and hearing loss?
Our work in Nepal shows that children who are malnourished in early childhood are approximately twice as likely to develop hearing loss as young adults. The data suggests that the association manifests in two ways. First, children who are too thin for their age — a type of acute malnutrition — are more likely to develop infections of all kinds, including ear infections, which can lead to hearing loss over time. Meanwhile, children who are too short for their age — meaning they are stunted or chronically undernourished — are more likely to develop hearing loss that’s entirely separate from infection. Because stunting often begins before birth, we suspect that malnutrition while still in the womb hinders development of the auditory system.
Why is the study such a big breakthrough?
This study elevates nutrition as an entirely new area for preventable hearing loss. Traditionally, prevention has been focused on such topics as vaccine-preventable illnesses, reducing noise exposure and avoiding medications that are toxic to the ear. Nutrition wasn’t even part of the conversation. But based on the results of this study, we now understand that there is a critical time period from fetal development through the preschool years in which good nutrition could reduce the risk of hearing loss later in life. Identifying this key window and having a clearer idea of why hearing loss is more common in low-resource settings will help focus efforts to prevent it in the first place.
Tell me about the scale of the study — and why southern Nepal?
The study represents a major effort to understand the impact of early-life nutrition on long-term health. Location is often key to understanding the broader impact of a study. We selected southern Nepal for this project because it’s representative of much of the Gangetic floodplain of South Asia, home to nearly 1 billion people. It’s also a region of the world where undernutrition is a pervasive problem.
More than 2,100 young adults in rural southern Nepal who had participated in a nutrition trial as preschool-aged children in the late 1980s underwent multiple health assessments 16 years later — including an ear and hearing evaluation.
How many people does hearing loss affect around the world? And what population is most affected?
Hearing loss is an underappreciated health disparity that affects over a billion people globally. The World Health Organization estimates that 80% of all people with hearing loss are living in low- and middle-income countries, where access to hearing care is often limited.
Hearing loss has a tremendous impact on people in every stage of life — from speech and language delays in early childhood to decreased school performance in school-aged children and limited job opportunities in adults. That’s why preventing it could have a truly beneficial impact on millions of lives.
Is hearing loss reversible for young adults who already suffer from it due to undernutrition?
We don’t know the answer to this question yet. Better nutrition is likely to be most important for preventing hearing loss from ever happening in the first place. We’re planning a study in the Bolivian Amazon that looks at whether stunted children who catch up in height are able to improve math and language skills. We believe hearing loss is fundamental to this relationship, and we’ll be observing for changes in hearing status over time in this study.
Now that we understand the link between nutrition and preventable hearing loss, what’s next? Will this change the way we prevent or treat hearing loss?
Moving forward, we need to study nutrition interventions focused on this crucial developmental period. We can also target undernourished children for hearing screening, knowing that they’re a high-risk population for developing hearing loss in the future.
Ultimately, addressing the global burden of hearing loss will require innovative strategies — not only for prevention but also diagnosis and treatment in remote regions with limited access to hearing care. For example, right now we’re doing exciting work in rural Alaska with new mobile screening technology and telemedicine to first identify individuals living with undiagnosed hearing loss, then connect them to the care they need. Stay tuned!
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