The massive, hidden burden of neurological disorders

A sudden sensation of numbness? The nagging headache that just won’t quit? That weird weakness in your leg? They’re all symptoms of neurological disorders — a family of conditions that affects more than half of the U.S. population, according to a new Yale study. 

And because these symptoms are often harbingers of health problems that are far more serious, researchers say they require a boost in public awareness. 

“People blow off warning signs,” said study author John Ney, an assistant professor of neurology at Yale School of Medicine. “I’ve had plenty of patients who experience a sudden onset of weakness or numbness down one side of the body, and say, ‘Well, this will probably go away. I’m going to go to bed and hope it’ll be gone the next day.’ And they wake up with a long-term disability, because they had a stroke that should have been addressed much earlier.”

The new study, published in the journal JAMA Neurology, revealed that about 180.3 million people in the U.S. (more than half of the population of roughly 332.7 million) are affected by disorders affecting nervous system health. Indeed, among that group these disorders were the leading cause of disability. Conditions posing the greatest risk of disability were stroke, Alzheimer’s disease and other dementias, diabetic neuropathy, and migraine.

The results were based on data from the broader Global Burden of Disease 2021, which collected data from 1990 to 2021. (In addition to Ney, researchers from the University of Washington; Emory University; and the American Academy of Neurology took part in the study.)

In a Q&A, Ney discussed the prevalence of neurological disorders, what might be driving their spike, and why the United States needs to pour more resources into combatting these conditions.

What are some of the neurological disorders included in the study? 

John Ney: Epilepsy, multiple sclerosis, stroke, and Alzheimer’s disease are all included in the current study. But we used a broader lens to parse this data, and we looked at other diseases that cause damage to the nervous system. So not just “neurological” diseases, but conditions like diabetes that cause substantial morbidity through neuropathy and other nervous system injury. There’s also a focus on neurodevelopmental disorders like autism and cerebral palsy, as well as idiopathic intellectual disabilities.

Were any of the findings surprising to you? 

Ney: One of the biggest findings is the overall prevalence of neurological disorders. So, 54% of the American population has a disorder that affects the nervous system. It doesn’t have to be one of the traditional neurological disorders. It may be neurological damage sustained from other disease processes, including diabetes. Globally, the prevalence rate was 43%, but the U.S. rate is actually higher. The United States has the highest prevalence of diseases affecting the nervous system of any country, whether high-income, low-income or middle-income. 

Any idea what’s driving these higher rates in the U.S.? 

Ney: Some of it is better recognition. Various advocacy organizations — including the American Academy of Neurology — and I think public health in general is putting a greater focus on neurological disorders and diseases affecting the nervous system. So, some of it is just putting out the message that if you have a condition that results in weakness, numbness, severe headache, and so on, these are not to be blown off. These are real problems, and you should seek medical care.

At the same time, we’re also getting better and better with neurophysiological studies, with imaging studies that can now document not just subjective complaints but objective anatomical and physiologic abnormalities.

What are common misperceptions people have about nervous system disorders? 

Ney: When we’re looking at trying to catalog how much damage is done, people always think about mortality — if a particular disorder is life-limiting. And typically the one that we think of most is cancer. Cancer gets a tremendous amount of attention because people lose their lives from it. 

Neurological disorders often are not life-limiting, but they cause a tremendous amount of disability. I think that’s probably the biggest thing that people don’t realize: they interfere with people’s ability to work and their economic output. They can require the input of caregivers, which represents an opportunity loss for the economy. These things need to be considered when we’re evaluating the importance of any condition. Even if it doesn’t kill you, it can still cause a large amount of morbidity and disability, and it’s something that needs to be addressed and should be prioritized.

And what are the most common neurological disorders?

Ney: The most common ones are what is known as “tension-type headaches.” People tend to think, “It’s just a headache. It’s not a big deal.” But even tension headaches can interfere with your ability to work. You may need to lie down. You can’t do anything at that point. 

Migraine headaches are a separate disorder. They affect up to 60 million Americans, closing in on 20% of the population. Even a single migraine headache can floor you and put you out of commission for a day or more. And that is a loss of quality of life. It’s also a loss of your ability to do anything useful during that day. 

When people think about maintaining their health, they often think in terms of diet, exercise, not drinking too much, getting vaccines. But what can people do to protect their neurological health?

Ney: I’m a headache specialist by profession, and a lot of the things that we think about with overall health certainly pertain to nervous system health. You need to recognize that nervous system health is an integral part of overall health. So, exercise, diet, getting a regular amount of sleep, trying to avoid unnecessary medications. All these things play into whether you’re going to have a headache the next day. 

For such conditions as stroke or Alzheimer’s disease exercise has been shown to be incredibly helpful in managing or mitigating risk. Diet, as we know, really impacts cerebrovascular diseases, and can make a substantial difference in the relative risk of having either a primary stroke or the next stroke down the line. 

Based on the study, what are some public health initiatives you’d recommend? 

Ney: A lot of it comes down to reshuffling priorities. In terms of basic science, this means trying to focus more on the mechanisms behind things like Alzheimer’s disease and motor neuron diseases. And for people who already have nervous system conditions, looking at things that help ameliorate them, like rehabilitation resources and new therapies.

Then there’s drug development and streamlining the process. Over the past 10 years, a huge number of therapies have come through the pipeline for migraine that we never dreamed about. We need to make sure that patients have access to all the new medications. Pharmaceutical and insurance companies play a role in ensuring these therapies go to the individuals who really need them. 

All these initiatives are incredibly important. It starts bench side — thinking about the mechanisms of and cause of disease — and then moves through funding and accessibility, which ultimately leads to the dissemination and implementation of viable, new therapies.