by Isabella Colonna and Matilde Leonardi, EAN Communications Committee Chair
Our paper of the month for April is the new study published in the Lancet Neurology on the Global, regional, and national burden of disorders affecting the nervous system, 1990-2021: a systematic analysis for the Global Burden of Disease Study 2021 (Lancet Neurol. 2024 Apr;23(4):344-381. doi: 10.1016/S1474-4422(24)00038-3. Epub 2024 Mar 14. Erratum in: Lancet Neurol. 2024 Mar 18;: PMID: 38493795; PMCID: PMC10949203).
The study found that neurological conditions are the leading cause of ill health and disability worldwide (measured in disability-adjusted life years – DALYs) and which estimates that over 3.4 billion people worldwide are affected. Since 1990, there has been an 18% rise in DALYs attributed to these conditions.
The paper is by the Global Burden of Diseases (GBD) Collaborator Network and its aim is to estimate the burden of neurological disorders, considering a larger group of GBD conditions, etiological categories and disease consequences, compared to the previous GBD analyses. A total of 37 neurological conditions are analysed, including neuro-developmental and neurological disorders, as well as neurological consequences (such as intellectual disability, epilepsy, neuropathy) of congenital, neonatal, metabolic or infectious diseases. The paper also includes COVID-19, which was not in previous GBD studies.
In 2021, an estimated 3.4 billion individuals (equivalent to 43.1% of the world population) were suffering from a neurological condition, contributing to 11.1 million deaths, as well as 168 million years lived with disability (YLDs), 275 million years of life lost (YLLs) and 443 million disability adjusted life-years (DALYs).
Neurological conditions ranked as the top contributor to global DALYs and YLLs, followed by cardiovascular diseases. Compared to 1990, there was an increase in global DALYs and YLLs attributed to neurological conditions, possibly due to global demographic trends and to increased exposure to environmental, metabolic and lifestyle risk factors, which may play crucial roles in non-communicable neurological diseases. However, age-standardised DALYs and YLLs decreased. The authors hypothesised that this reduction may be due to increased public awareness of stroke, improved acute stroke treatments, global vaccination efforts, disease-preventive strategies for many neuroinfectious diseases, as well as improved access to prevention and treatment for neurological conditions. This datum is important for the evaluation of effects of public health intervention and increased care for neurological disorders.
In terms of regional differences, age-standardised DALYs were highest in western and central sub-Saharan Africa, and lowest in Australasia and high-income Asia-Pacific countries. These differences were even more pronounced when considering children younger than five years, due to the higher incidence of birth-related complications and infections in these countries. Moreover, it has been reported that 81.9% of deaths and 84.7% of DALYs due to neurological conditions occurred in low- to middle-income countries.
In 2021 the ten neurological conditions contributing to the highest number of DALYs (in ranking order) are stroke, neonatal encephalopathy, migraine, Alzheimer’s disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.
For Central Europe the ranking is different, having the following order: stroke, migraine, dementia, diabetic neuropathy, nervous system cancer, autism spectrum disorders, epilepsy, traumatic brain injuries, preterm birth and neonatal encephalopathy
When considering different age spans, the three worldwide leading causes of DALYs were: neonatal encephalopathy, meningitis and neural tube defects for children younger than five years; migraine, neurological complications due to preterm birth and epilepsy for individuals aged 5-19 years; stroke, migraine and diabetic neuropathy for adults aged 20-59 years; stroke, dementias and diabetic neuropathy for the age span of 60-79 years; and stroke, dementias and Parkinson’s disease for those over 80 years old. All these age-specific DALY rates were similar or higher in males than in females for all age groups, with the exception of those aged 90 years and older.
The authors identified 18 risk factors for stroke, four for encephalitis and meningitis, three for Alzheimer’s disease and other dementias, and one each for idiopathic epilepsy, Parkinson’s disease, multiple sclerosis and idiopathic intellectual disability. The most relevant risk factor for stroke was high systolic blood pressure; other risk factors included ambient particulate matter as well as household air pollution. Smoking was linked to increased DALYs for stroke, dementias, and multiple sclerosis. Higher fasting blood glucose and alcohol abuse were associated with increased risk for dementias and idiopathic epilepsy, respectively.
In summary, this work highlights that disorders affecting the nervous system are the leading cause of overall disease burden worldwide. Considering differences across the lifespan and within countries, tailored treatment and prevention strategies, public health plans, and promotion of research into novel interventions are urgently needed in order to face the growing burden of neurological disorders.
From the EAN perspective, the outcomes of this study are very relevant as they show the need to increase global collaboration to increase brain health and neurological care, not only in Europe, but in collaboration with all regions of the world. The EAN is ready to make more in-depth evaluations on the consequences of these new data that highlight the need to reduce the global burden of neurological disorders, as also indicated by the WHO Global Action Plan on epilepsy and other neurological disorders that the EAN is implementing in Europe, as well as to support more prevention, diagnosis, care and research in neurology.
The figure below shows the ranking of age-standardised DALY rates for all conditions with neurological health loss by GBD region in 2021:
Read the full paper here.
