We are living in a rapidly changing landscape in terms of global public health. On one hand, the immense increase in and ageing of the world’s population, mass migration of people from rural to urban areas, and unhealthy lifestyles—either by choice or by circumstance—are negatively affecting the overall health of the planet. On the other hand, medical advances such as vaccines, antibiotics, and new medications, and renewed emphasis on workplace safety, have benefitted global health. These balancing influences perhaps have the most effect on neurological diseases, which affect many different daily functions and therefore have a disproportionately large effect on global health.
However, in The Lancet Neurology, Valery Feigin, Theo Vos, and colleagues from the GBD 2015 Neurological Disorders Collaborator Group1 present evidence that the overall global burden of neurological disease has been previously underestimated. Feigin, Vos, and co-investigators reclassified some important neurological illnesses within the Global Burden of Disease 2015 (GBD 2015) Study, a large composite database estimating burden of disease, including prevalence, deaths, and disability-adjusted life-years (DALYs) of 315 diseases and injuries for 195 countries and territories from 1990 to 2015. The investigators provided a more accurate representation of the overall effect of neurological diseases on global health simply by moving several diseases from other categories to that of neurological disorders; ie, stroke from cardiovascular diseases, brain and nervous system cancer from cancers, and diseases such as encephalitis, meningitis, and tetanus from infectious diseases. These changes alone resulted in neurological disorders representing the largest cause of DALYs in 2015 (250·7 [95% uncertainty interval (UI) 229·1 to 274·7] million, equivalent to 10·2% of global DALYs) and the second-largest cause of global deaths (9·4 [9·1 to 9·7] million], equivalent to 16·8% of global deaths). The number of DALYs resulting from neurological diseases was even more than those resulting from all injuries. These findings have important repercussions for global public health assessments and health resource allocation.
Some of the findings are not surprising. Headaches represented the most prevalent neurological disorders: tension-type headache (1505·9 [95% UI 1337·3 to 1681·6] million cases), migraine (958·8 [872·1 to 1055·6] million), and medication overuse headache (58·5 [50·8 to 67·4] million). The highest burden of communicable neurological diseases and epilepsy occurred in the lowest socioeconomic regions of the world, commensurate with poor access to sanitation, vaccines, antibiotics, and other medicines, and incidence of meningitis was highest in western sub-Saharan Africa—the so-called meningitis belt. However, worldwide there was actually an overall decrease in communicable neurological disorders from 1990 to 2015. As long as neurological infections due to pathogens such as Zika and West Nile viruses and increasing antimicrobial resistance can be controlled, this downward trend in communicable neurological diseases is promising. However, the prevalence of and DALYs attributable to non-communicable neurological diseases increased because of the growing and ageing global population. In particular, Alzheimer’s disease and other dementias had increases in prevalence and mortality, especially in some high-income regions.
Notably, although overall age-standardised DALYs, and deaths from all neurological disorders decreased between 1990 and 2015, the number of people with neurological diseases increased substantially, with the number of deaths from neurological disorders increasing by 36·7%, and the number of DALYs by 7·4%. Neurological diseases that more commonly occur in elderly people, such as Alzheimer’s disease and other dementias, Parkinson’s disease, and neurological cancers, are probably driving these overall neurological disease indices. The findings from Feigin, Vos, and co-authors’ study suggest that the absolute number of people affected by (or dying from) neurological disease will continue to increase as the global population continues to grow and age. This trend could be augmented by the increasing incidence of stroke in low-income countries, despite the success in curbing stroke in high-income countries.
The GBD 2015 Neurological Disorders Collaborator Group present a tremendous amount of data in a concise format, but three overriding points emerge from their assessment. First, the reduction in the burden of communicable neurological diseases in high-income and middle-income countries emphasises the need to replicate these efforts in low-income countries, which have the highest occurrence of neurological infections and secondary causes of epilepsy. Second, the decrease in burden of illness due to stroke and other cerebrovascular diseases in high-income countries might have resulted from better control of high blood pressure, cessation of tobacco use, and earlier interventions in the setting of acute stroke. This finding suggests that these successes can be replicated in middle-income and low-income countries if enough public health funding is put behind these efforts. Third, in both low-income and high-income countries, the overall burden of neurological disease is inevitably going to continue to increase as populations increase and grow older. Age-related neurological disorders, such as Alzheimer’s disease and other dementias, Parkinson’s disease, and neurological cancers, are going to be the large neurological public health struggles in the future.
Given the worldwide shortage of neurologists and other neurological specialists, the report by Feigin, Vos, and co-authors sends out an important warning for the global public health community—pay heed to the increasing, and increasingly important, role of neurological disease in terms of public health resource allocation. Public health professionals and health-care policy makers must now implement much-needed public health interventions to address the growing need for neurological care across all ages and socioeconomic classes.
I declare no competing interests.