Greater Global Burden of Neurological Conditions

Globally, the prevalence and impact of neurological conditions, such as stroke, Alzheimer’s disease, and meningitis, have significantly increased over the past three decades due to the expanding and aging global populace, alongside heightened exposure to environmental, metabolic, and lifestyle risk factors. According to a recent extensive analysis from the Global Burden of Disease, Injuries, and Risk Factors Study (GBD) 2021, published in The Lancet Neurology journal, approximately 3.4 billion individuals worldwide encountered a neurological condition in 2021.

The analysis indicates a substantial 18% rise in the overall burden of disability, illness, and premature death—measured as disability-adjusted life years (DALYs)—attributed to neurological conditions over the past 31 years, escalating from roughly 375 million years of healthy life lost in 1990 to 443 million years in 2021.

While the absolute number of DALYs escalates primarily due to global population growth and aging, when demographics’ impact is adjusted through age-standardization, rates of DALYs and deaths resulting from neurological conditions have diminished by around a third (27% and 34% respectively) worldwide since 1990—largely driven by enhanced awareness, vaccination, and global prevention endeavors for certain conditions such as tetanus (witnessing a 93% decrease in age-standardized rates of DALYs), meningitis (62% decrease), and stroke (39% decrease).

In 2021, the top 10 contributors to neurological health loss encompassed stroke, neonatal encephalopathy, migraine, Alzheimer’s disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications from preterm birth, autism spectrum disorder, and nervous system cancers. Neurological consequences of COVID-19, including cognitive impairment and Guillain-Barré syndrome, ranked 20th, amounting to 2.48 million years of healthy life lost in 2021.

Tension-type headaches and migraines emerged as the most prevalent neurological disorders in 2021, with around 2 billion and 1.1 billion cases respectively. Remarkably, diabetic neuropathy emerged as the fastest-growing neurological condition.

The study underscores the imperative to address neurological disorders effectively through culturally acceptable, affordable prevention, treatment, rehabilitation, and long-term care strategies, given their status as the leading cause of overall disease burden globally, with case numbers soaring by 59% worldwide since 1990.

The authors underscore that, as of 2017, merely a quarter of nations globally allocated a distinct budget for neurological conditions, with approximately half having clinical guidelines. Furthermore, the distribution of medical professionals caring for individuals with neurological conditions is notably disparate worldwide, with high-income countries boasting 70 times more neurological experts per 100,000 individuals than LMICs.

Emphasizing the importance of prevention “Given the absence of cures for many neurological conditions and the limited access to medical care, comprehending modifiable risk factors and the potentially preventable burden of neurological conditions is crucial in combating this global health crisis,” expressed co-lead author Dr. Katrin Seeher, a Mental Health Specialist at WHO’s Brain Health Unit.

The study quantified the proportion of nervous system burden deemed preventable by addressing known risk factors for various conditions, including stroke, dementia, multiple sclerosis, Parkinson’s disease, encephalitis, meningitis, and intellectual disability.

The analysis suggests that modifying 18 risk factors throughout an individual’s lifetime—most notably high systolic blood pressure (accounting for 57% of DALYs)—could potentially prevent 84% of global DALYs attributed to stroke.

Additionally, estimates indicate that managing lead exposure could diminish the burden of intellectual disability by 63%, while normalizing high fasting plasma glucose levels could lower the burden of dementia by approximately 15%.

“The global neurological burden is escalating rapidly and will exert even greater strain on healthcare systems in the forthcoming decades,” stated co-senior author Dr. Valery Feigin, Director of Auckland University’s National Institute for Stroke and Applied Neuroscience in New Zealand. “Yet, many existing strategies for mitigating neurological conditions exhibit limited efficacy or are inadequately implemented, as evidenced by some of the most rapidly expanding yet largely preventable conditions like diabetic neuropathy and neonatal disorders. With no cure available for many other conditions, there is a pressing need for increased investment and research into innovative interventions and potentially modifiable risk factors.”

Neurological conditions encompass infectious and vector-borne diseases and injuries, as well as non-communicable diseases and injuries, necessitating diverse prevention and treatment strategies throughout life. We trust that our findings can furnish policymakers with a comprehensive understanding of the impact of neurological conditions on both adults and children, thereby informing more targeted interventions at the national level and guiding ongoing awareness and advocacy endeavors globally.

Dr. Jaimie Steinmetz, Lead Author, IHME

Despite these significant findings, the authors acknowledge several limitations. While they endeavored to encompass all nervous system health losses, certain conditions were omitted due to the inability to isolate the neurological component, such as infections like HIV, which exert substantial impacts in many regions worldwide. Furthermore, the study’s estimates are constrained by the quantity and quality of data, particularly in LMICs.

In a related commentary, Professor Wolfgang Grisold, President of the World Federation of Neurology, London, UK (not involved in the study), remarks, “This significant new GBD report underscores that the burden of neurological conditions surpasses prior estimations. In the forthcoming iteration, greater attention should be devoted to neuromuscular diseases, the ramifications of cancer on the nervous system, and neuropathic pain. Nonetheless, comparing the disability induced by conditions with episodic occurrences versus those causing permanent and progressive diseases will remain challenging, given the substantial variability in individual impacts.”

For more information: Global, regional, and national burden of disorders affecting the nervous system, 1990-2023: a systematic analysis for the Global Burden of Disease Study 2021, The Lancet Neurology Journal, http://doi.org/10.1016/s1474-4422(24)00038-3