Upwards Of 3 Billion People Live With Neurological Disorders

The analysis revealed that neurological conditions were responsible for 443 million years of healthy life lost due to illness, disability, and premature death, putting them ahead of cardiovascular disease as the top contributors to the global disease burden. The top 10 contributors to the loss of neurological health were migraine, stroke, neonatal encephalopathy, Alzheimer’s disease, dementias, meningitis, epilepsy, diabetic neuropathy, autism, nervous system cancers, neurological complications from preterm births, cognitive impairment, and Guillain-Barre syndrome. 

The most prevalent neurological conditions were migraines with around 1.1 billion cases, and tension-type headaches with close to 2 million cases. However, diabetic neuropathy is the fastest growing of all neurological conditions, and over 80% of neurological deaths and health loss were revealed to occur in low and middle-income countries. 

“The number of people with diabetic neuropathy has more than tripled globally since 1990, rising to 206 million in 2021,” said study co-senior author Dr. Liane Ong, from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington. “This is in line with the increase in the global prevalence of diabetes.”

Stroke was the top contributor to age standardized DALYs in 10/21 GBD regions. There were more than 23 million cases of COVID-19 with long-term cognitive symptoms of Guillain-Barre syndrome accounting for 57% of all infectious neurological disease cases. Diabetic neuropathy increased by 92%, neurological complications from neonatal sepsis increased by 70%, and cerebral malaria increased by 54% which are all largely preventable and were the fastest-growing causes of age-standardized DALYs over the last three decades.

Tetanus, rabies, meningitis, stroke, neural tube defects, neurocysticercosis, encephalitis and neonatal encephalopathy all had a 25% or larger decline in age standardized DALYs reflecting improvements in prevention, care and research.

Overall, age standardized DALYs for neurological conditions were lower among females than men.  However, neurological consequences of COVID-19, multiple sclerosis, and migraine were higher in females globally, and attention deficit hyperactivity disorder (ADHD), traumatic brain injury, and autism spectrum disorder were twice as high in males globally.

High-income areas had the best neurological health, having a rate of DALYs and death under 3,000 and 65 per 100,000 respectively, with stroke, migraine, dementia, diabetic neuropathy, and autism spectrum disorders accounting for the most health loss. In worse off regions, the rate of DALYS and deaths were up to 5 times higher, over 7,000 and 198 per 100,000 people respectively, with stroke, neonatal encephalopathy, dementia, and meningitis being the biggest drivers of healthy years of life lost. 

“Every country now has estimates of their neurological burden based on the best available evidence,” said lead author Dr Jaimie Steinmetz from IHME. “As the world’s leading cause of overall disease burden, and with case numbers rising 59% globally since 1990, nervous system conditions must be addressed through effective, culturally acceptable, and affordable prevention, treatment, rehabilitation, and long-term care strategies.”

To draw attention to the fact that neurological disorders can occur at any stage of life, for the first time the GBD 2021 Nervous System Disorders Collaborators studied neurodevelopmental disorders and neurological conditions in children to reveal that they were responsible for 18% of all DALYs in 2021, representing 80 million years of healthy life lost, globally. Neurodevelopmental and pediatric conditions were estimated to represent almost a fifth of the total neurological global burden, being the equivalent of 80 million years of healthy life lost. 

“Nervous system health loss disproportionately impacts many of the poorest countries partly due to the higher prevalence of conditions affecting neonates and children under 5, especially birth-related complications and infections,” said Dr. Tarun Dua, Unit Head of WHO’s Brain Health unit and one of the co-senior authors of the study. “Improved infant survival has led to an increase in long-term disability, while limited access to treatment and rehabilitation services is contributing to the much higher proportion of deaths in these countries.”

“Because many neurological conditions lack cures, and access to medical care is often limited, understanding modifiable risk factors and the potentially avoidable neurological condition burden is essential to help curb this global health crisis,” said co-lead author Dr Katrin Seeher, Mental Health Specialist at WHO’s Brain Health Unit. 

The analysis indicates that modifying 18 risk factors over a lifetime, specifically high blood pressure which is 57% of the DALYs, could prevent 84% of the global DALYs from stroke alone. Estimates also suggest that controlling exposure to lead could reduce the burden of intellectual disability by 63%, and reducing high fasting plasma glucose levels to normal levels could decrease the burden of dementia by 15%.

“The worldwide neurological burden is growing very fast and will put even more pressure on health systems in the coming decades,” said co-senior author Dr Valery Feigin, Director of Auckland University’s National Institute for Stroke and Applied Neuroscience in New Zealand. “Yet many current strategies for reducing neurological conditions have low effectiveness or are not sufficiently deployed, as is the case with some of the fastest-growing but largely preventable conditions like diabetic neuropathy and neonatal disorders. For many other conditions, there is no cure, underscoring the importance of greater investment and research into novel interventions and potentially modifiable risk factors.”

“Nervous system conditions include infectious and vector-borne diseases and injuries as well as non-communicable diseases and injuries, demanding different strategies for prevention and treatment throughout life,” said Steinmetz “We hope that our findings can help policymakers more comprehensively understand the impact of neurological conditions on both adults and children to inform more targeted interventions in individual countries, as well as guide ongoing awareness and advocacy efforts around the world.” 

“This important new GBD report highlights that the burden of neurological conditions is greater than previously thought. In the next iteration, more attention should be given to neuromuscular diseases, the effects of cancer in the nervous system, and neuropathic pain. Comparing the disability caused by conditions with episodic occurrence versus those that cause permanent and progressive disease will remain challenging, because the effects on the individuals vary substantially,” said Professor Wolfgang Grisold, President of the World Federation of Neurology, London, UK (who was not involved in the study) in a commentary note.