Undiagnosed Nerve Disorders May Be Widespread Among Americans, Doctors Warn

A constant feeling of strange tingling and numbness along a person’s legs might be much more common than assumed in some parts of the U.S., new research out Wednesday suggests. Researchers have found evidence that a substantial majority of older adults in Flint, Michigan are experiencing neuropathy, an uncomfortable ailment caused by nerve damage that can raise the risk of other serious health problems such as infections and falls. Often, these patients were even unaware that they had it.

The research was led by scientists from the University of Michigan. In 2021, they began the Flint Neuropathy Study, hoping to better understand a form of the condition known as distal symmetric polyneuropathy, or DSP. DSP is thought to be the most common form of peripheral (outside of the brain) neuropathy and is characterized by numbness, tingling, and pain that begins in the feet but can spread elsewhere.

“This study makes it clear that what we know about neuropathy and the number of people affected by it likely does not represent all the U.S. population.”

They also wanted to specifically focus on Flint due to the lack of attention that such communities tend to receive from the scientific world. The town infamously suffered a grave public health crisis during the 2010s, which exposed residents to potentially dangerous levels of lead and disease-causing Legionella bacteria via their drinking water. 

“Most well-conducted research studies looking at how many people have neuropathy and the impact that it has on their lives have overlooked places like Flint. Minority and low-income communities are often under-represented in clinical research,” Melissa Elafros, a U-M researcher and lead investigator of the project, told Gizmodo in an email. “So, we launched the Flint Neuropathy Study to see if what is known about neuropathy is true for our patients in Flint.”

Elafros and her team asked people over the age of 40 who were receiving routine outpatient care at the Hurley Medical Center in Flint to take part in the study. Two hundred people agreed to enroll, while 169 were able to complete all three study visits. The first peer-reviewed findings from the study, which is still ongoing, were published Wednesday in the journal Neurology.

DSP can have many causes, but diabetes is a well-known risk factor for it. And since lower-income, minority communities tend to have higher rates of diabetes, the researchers were expecting that the same would be true for neuropathy. But even they were surprised by how common it was in their patients.

“In the U.S. the accepted prevalence rate for neuropathy is 13.5% meaning that out of every 100 people, 13 have neuropathy. Among the adults that participated in our research study, we found that 73 out of every 100 had neuropathy. That’s a huge difference!” Elafros said. What’s worse is that three-fourths of these patients were completely in the dark about their condition, having previously been undiagnosed.

“Because there is no cure for neuropathy, most of our management consists of helping to control pain and counsel patients to prevent falls and foot trauma that can lead to cuts, infections, and, even worse, amputations,” Elafros noted. “If patients and their doctors don’t realize that someone has neuropathy, none of this happens.”

The findings do come from a sample of patients at a single outpatient clinic. So it’s possible that the true rate of neuropathy among older adults living in Flint might be lower. But given the wide disparity between their figures and national estimates, the team believes it’s likely that neuropathy and related conditions are being substantially underestimated and unaddressed in many parts of the country similar to Flint. And as noted, people in the study had high rates of often uncontrolled diabetes and obesity, for instance, which might be driving the high rates of neuropathy in this group.

“This study makes it clear that what we know about neuropathy and the number of people affected by it likely does not represent all the U.S. population,” she said.

The team is still working with patients and doctors at the Hurley Medical Center to learn more about why people’s diabetes is often uncontrolled and they’re looking for ways to improve the screening of neuropathy during primary care visits. Last year, Elafros and her team also received additional funding from the National Institutes of Health to expand their project, and they’re already begun to partner with primary care providers at the McLaren Flint hospital to study the rate of neuropathy and potential risk factors among patients there.

“We are working to expand out into the community so we can improve quality of life for those with neuropathy and prevent those at risk from developing it,” Elafros said.