Q&A: The global burden of nervous system disorders

This transcript has been lightly edited for clarity

What are the key findings of your research?

Our goal was to quantify all nervous system health loss globally from as many different conditions as possible. And we found that in 2021, about 40% of the global population experienced some form of neurological health loss, which is a huge proportion of the global population.

We also look at a measure that’s called disability-adjusted life years, which is a combination of health loss that is experienced by people living with these conditions as well as accounting for deaths due to these conditions. And we found that the nervous system grouping is the largest cause of disability-adjusted life years in the GBD, or Global Burden of Disease study.

What is new about this research?

For the first time, in this analysis, we were able to include neurodevelopmental conditions and other early life conditions, for example, brain damage due to birth trauma. We were also able to include neurological consequences of diseases such as diabetes, so nerve damage due to diabetes and cognitive impairment due to COVID-19.

What neurological conditions lead to the greatest health loss?

Some of the conditions that lead to the largest amount of health loss include stroke, dementia, brain injury from birth trauma, epilepsy, neurological consequences of preterm birth, or meningitis. I think what’s really striking about this is that these conditions can occur across the human lifespan.

So some of these conditions are most common in the early life or neonatal period, all the way through older age.

Which regions are particularly affected, and why is that?

Over 80% of health loss and deaths due to these neurological conditions occurs in low- and middle-income countries compared to high-income countries. So, for example, we see some of the lowest rates in Australia, Asia, and high-income Asia Pacific and some of the highest rates in Western and central sub-Saharan Africa.

And we know from previous research that wasn’t part of this analysis that there’s very inequitable distribution of neurological care. So, for example, the density of the trained workforce in high-income locations is about 70 times higher than in lower-resource settings, in spite of the fact that we see much higher burden in lower-resource settings.

How should policymakers and the global health community respond to the research findings?

Because we show that the majority of burden is experienced in low- and middle-income settings, there should be more equitable distribution of services, for example, immediate care or rehabilitation. From the conditions that we’ve analyzed as part of this work, we also looked at risk factors for neurological conditions, so, for example, exposure to air pollution or hypertension, and policymakers could target interventions toward some of these key risk factors to decrease the likelihood of these diseases occurring in the first place.

What, if anything, is the good news from your research?

We did show that health loss from this group of conditions has increased over the past 30 years from 1990 to 2021. But this is mostly due to aging and growing populations. So I think, encouragingly, if we remove the effects of demographics, we actually see improvement for neurological health loss over the same time period. This is largely due to decreases in death from conditions such as stroke and some early life and infectious conditions as well. So we are seeing progress.