In March 2024 WHO shared that a “major new study” in The Lancet Neurology reveals that more than 3 billion people worldwide were living with a neurological condition in 2021. The paper estimates nervous system health loss caused by a total of 37 conditions and their associated risk factors at global, regional, and national levels between 1990 and 2021. The authors conclude that effective prevention, treatment, and rehabilitation strategies are “needed” to tackle the “leading cause of overall disease burden in the world”.
Neurological conditions
As the leading cause of “ill health and disability” conditions can affect the nervous system “throughout life” with consequences an individual’s cognitive, sensory, socioemotional, and motor function and behaviour abilities. Neurological conditions are a “diverse group” that include congenital and neurodevelopmental disorders, cerebrovascular and neurodegenerative diseases, neurological infections, and more.
The authors reflect that, although increased life expectancy is “arguably one of the greatest achievements of health systems around the world”, this increase has led to increases in age-related neurological disorders, such as Alzheimer’s and other dementias, stroke, and Parkinson’s. This increase demands global health policies “not only to focus on survival but also to minimise health loss due to disability by promoting function and independence”.
However, as neurological burden is not entirely associated with population ageing, the authors deem it important to quantify the “overall health loss” associated with nervous system conditions throughout the lifespan. Therefore, they sought to estimate the burden of disorders and conditions that affect the nervous system with an expanded group of Global Burden of Disease, Injuries, and Risk Factors Study (GBD) conditions, cause categories, and disease consequences.
What does the study find?
The findings suggest that around 3.4 billion individuals had a condition affecting the nervous system in 2021. This corresponds to 43.1% of the world’s population. The total conditions caused 11.1 million deaths and contributed to 168 million YLDs (year of healthy life lost to due disability) as well as 275 million YLLs (year of health life lost due to mortality).
“With a total of 443 million DALYs, this expanded nervous system category was the top-ranked contributor to global DALYs and YLLs in BGD 2021, followed by cardiovascular diseases.”
Age-standardised DALY rates were highest in western sub-Saharan Africa with 8,190.6 per 100,000 people) and central sub-Saharan African 7,967.5 per 100,000 people). They were lowest in Australasia with 2,88.2 per 100,000 people and “high income Asia Pacific” with 2,984.6 per 100,000 people. The article describes “large differences” for children younger than 5 years. For example, DALY rates for this group were roughly “18-fold higher in western sub-Saharan Africa”, driven by conditions such as neonatal encephalopathy, meningitis, and encephalitis.
The authors use World Bank income levels to reveal that 81.9% of deaths and 84.7% of DALYs that were attributable to neurological conditions were in LMICs. They describe their efforts as the “most comprehensive estimate of neurological burden globally” with the inclusion of conditions that had not previously been captured. These include Guillain-Barré syndrome, neurocysticercosis, rabies, and neuroblastoma and other peripheral nervous cell tumours, which contributed 2.14 million DALYs (0.5% of the total).
“Nervous system health loss disproportionately affected people in LMICs, partly due to higher prevalence of conditions affecting neonates and children younger than 5 years (especially birth-related complications and infections). Increased survival in neonates is unfortunately accompanied by an increase in the long-term disability from neurological complications of these conditions.”
Furthermore, access to treatment and rehabilitation services is “limited by little availability or existence of specialised services and workforces”. The authors suggest that the high proportion of deaths in LMICs compared with HICs is “probably related to poorer access to high-quality services and nervous system specialists”.
While nervous system conditions contribute to more DALYs in males they have a “higher prevalence in females”, which is “mostly attributable to migraine and tension-type headache”. Disease burden “generally” increases with age. However, different patterns emerged for different conditions, which emphasises the need for “tailored interventions and prevention strategies across the lifespan”.
What role do vaccines play?
The authors assume that observed reductions in DALYs were “probably driven” by global vaccination and disease-prevention efforts. This includes targets such as tetanus, rabies, meningitis, neurocysticercosis, and encephalitis. For example, they estimate a reduction of 17.8% in encephalitis DALYs can be “partly” attributed to Japanese encephalitis vaccination and improved access to health care.
“The substantial decrease in global deaths from tetanus because of vaccination strategies emphasises the profound value of vaccination prevention campaigns.”
Additional benefits are attributed to the “promotion and enforcement of folic acid supplementation” and “fortification of grain products”.
The key message
The authors conclude that “acute and chronic conditions affecting the nervous system are diverse”, which means that they need “different public health strategies for prevention and treatment across the life course”. Resources should “span the entire care continuum” from prevention to palliation. On one hand, improved population-level preventative strategies for neurological infections and birth-related neurological sequalae can “affect many lives”. On another, zoonotic diseases emphasise the importance of “close collaboration across sectors.
Dr Tedros Adhanom Ghebreyesus commented on the study, suggesting that it should “serve as an urgent call to action” to “scale up targeted interventions to allow the growing number of people living with neurological conditions to access the quality care, treatment, and rehabilitation they need”.
“It is more important than ever to ensure brain health is better understood, valued, and protected, from early childhood to later life.”
While vaccines can play an important role in tackling these conditions at a preventative level, how might they fit into care capabilities in the future? Do join us at the Congress in Washington to discuss this, and more questions, by getting your tickets here, or subscribe for more insights!
